Electrochemical separators with inserted conductive layers

ABSTRACT

Disclosed are electrochemical cells including a composite separator capable of changing the performance of the cell by a) changing the internal electric field of the cell, b) activating lost active material, c) providing an auxiliary current collector for an electrode and/or d) limiting or preventing hot spots and/or thermal runaway upon formation of an electronic short in the system. An exemplary composite separator includes at least one electronically conducting layer and at least one electronically insulating layer. Another exemplary composite separator includes an electronically conducting layer and a solid ionic conductor. Also disclosed are methods for detecting and managing the onset of a short in an electrochemical cell and for charging an electrochemical cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 61/905,678, filed Nov. 18, 2013; U.S. ProvisionalApplication No. 61/938,794, filed Feb. 12, 2014; and U.S. ProvisionalApplication No. 61/985,204, filed Apr. 28, 2014 and U.S. ProvisionalApplication No. 62/024,104, filed Jul. 14, 2014; all of which are herebyincorporated by reference in their entireties to the extent notinconsistent herewith.

BACKGROUND OF INVENTION

Over the last few decades revolutionary advances have been made inelectrochemical storage and conversion devices expanding thecapabilities of these systems in a variety of fields including portableelectronic devices, air and space craft technologies, passenger vehiclesand biomedical instrumentation. Current state of the art electrochemicalstorage and conversion devices have designs and performance attributesthat are specifically engineered to provide compatibility with a diverserange of application requirements and operating environments. Forexample, advanced electrochemical storage systems have been developedspanning the range from high energy density batteries exhibiting verylow self-discharge rates and high discharge reliability for implantedmedical devices to inexpensive, light weight rechargeable batteriesproviding long runtimes for a wide range of portable electronic devicesto high capacity batteries for military and aerospace applicationscapable of providing extremely high discharge rates over short timeperiods.

Despite the development and widespread adoption of this diverse suite ofadvanced electrochemical storage and conversion systems, significantpressure continues to stimulate research to expand the functionality ofthese systems, thereby enabling an even wider range of deviceapplications. Large growth in the demand for high power portableelectronic products, for example, has created enormous interest indeveloping safe, light weight primary and secondary batteries providinghigher energy densities. In addition, the demand for miniaturization inthe field of consumer electronics and instrumentation continues tostimulate research into novel design and material strategies forreducing the sizes, masses and form factors of high performancebatteries. Further, continued development in the fields of electricvehicles and aerospace engineering has also created a need formechanically robust, high reliability, high energy density and highpower density batteries capable of good device performance in a usefulrange of operating environments.

Many recent advances in electrochemical storage and conversiontechnology are directly attributable to discovery and integration of newmaterials for battery components. Lithium battery technology, forexample, continues to rapidly develop, at least in part, due to thediscovery of novel electrode and electrolyte materials for thesesystems. The element lithium has a unique combination of properties thatmake it attractive for use in an electrochemical cell. First, it is thelightest metal in the periodic table having an atomic mass of 6.94 AMU.Second, lithium has a very low electrochemical oxidation/reductionpotential (i.e., −3.045 V vs. NHE (normal hydrogen referenceelectrode)). This unique combination of properties enables lithium basedelectrochemical cells to have very high specific capacities. State ofthe art lithium ion secondary batteries provide excellentcharge-discharge characteristics, and thus, have also been widelyadopted as power sources in portable electronic devices, such ascellular telephones and portable computers. U.S. Pat. Nos. 6,852,446,6,306,540, 6,489,055, and “Lithium Batteries Science and Technology”edited by Gholam-Abbas Nazri and Gianfranceo Pistoia, Kluer AcademicPublishers, 2004, which are hereby incorporated by reference in theirentireties, are directed to lithium and lithium ion battery systems.

Advances in electrode materials, electrolyte compositions and devicegeometries continue to support the further development of Li basedelectrochemical systems. For example, U.S. Patent ApplicationPublication US2012/0077095, published on Mar. 29, 2012, andInternational Patent Application publication WO 2012/034042, publishedon Mar. 15, 2012, disclose three-dimensional electrode array structuresfor electrochemical systems including lithium batteries.

Despite substantial advances, practical challenges remain in connectionwith the continued development of Li and Zn based electrochemicalsystems. A significant issue, for example, relates to dendrite formationin secondary zinc and lithium based systems and to electronicconductivity loss in Si anode and sulfur or air cathode lithium ionbatteries. It is generally known that Li or Zn deposition in manyelectrolytes is highly dendritic which make these systems susceptible toproblems involving shorting, mechanical failure and thermal runaway.Safety concerns relating to dendrite formation are currently a barrierto implementation of metal Li and Zn anodes in rechargeable systems. Anumber of strategies have been pursued to address safety in connectionwith dendrite formation, particularly in the context of secondarybatteries, including development of non-lithium anodes and internalsafety systems able to monitor in real time problems associated withdendrite formation.

As will be generally recognized from the foregoing, a need currentlyexists for electrochemical systems, such as lithium based or alkalinebased batteries, flow batteries, supercapacitors and fuel cells,exhibiting electrochemical properties useful for a range ofapplications. Specifically, lithium electrochemical systems capable ofgood electrochemical performance and high versatility for both primaryand secondary lithium based batteries are needed.

SUMMARY OF THE INVENTION

Thermal runaway in batteries is triggered by portions of the batteryreaching excessive temperatures and can occur as a result of an internalor external electrical or electronical short between the positive andthe negative electrode. Causes of internal shorts include dendrites orforeign materials in the battery. In one aspect, the disclosure provideselectrochemical cells including a composite separator capable oflimiting or preventing hot spots and/or thermal runaway upon formationof an electronic short in the system. These electrochemical cells canenhance the safety of the cell and also prolong the cycle life. Thedisclosure also provides electrochemical cells including a compositeseparator which allows monitoring of cell performance and earlydetection of internal short formation. The disclosure also provideselectrochemical cells including a composite separator which allowscontrol of the cell. Methods for reducing dendrite growth and fordetection of electronical shorts are also provided.

In an embodiment, the disclosure provides an electrochemical cellcomprising: a positive electrode; a negative electrode; one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and a composite separator comprising at least oneelectronically insulating layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein thepresence of the said electronically conductive layer(s) of the saidseparator affects the performance of the electrochemical cellperformance upon formation of an electronical short between any of thesaid electrodes or the said electronically conductive layer.

In an embodiment, the disclosure provides electrochemical cellscomprising a positive electrode, a negative electrode, one or moreionically conductive electrolytes positioned between said positiveelectrode and said negative electrode, and a composite separatorcomprising at least one electronically insulating layer and at least oneelectronically conductive layer. In a further embodiment, the disclosureprovides electrochemical cells comprising a positive electrode, anegative electrode, one or more ionically conductive electrolytespositioned between said positive electrode and said negative electrode,and a composite solid electrolyte comprising a solid electrolyte and atleast one electronically conductive layer. The composite separators arepermeable to ionic charge carriers, but are not electronicallyconductive across their thickness.

In a further embodiment, the disclosure provides a composite solidelectrolyte for an electrochemical cell comprising at least anelectronically non-conductive layer, at least a porous layer ofelectronically conductive material and at least a group of fibers orparticles filling the pores/holes of the porous layer.

In an aspect, the electronically conductive layer of the separatormitigates the effects of internal and/or external shorts between thepositive and negative electrode. In embodiments, the cell eithercontinues operating or fails without any thermal runaway′ in the eventof a short. In an embodiment, contact of a dendrite structure with theelectronically conductive separator modifies the redox reactions takingplace in the cell and the cell voltages. In an embodiment, themodification of the redox reactions and cell voltages is such thatdendrite growth is not favored.

In an aspect, the electronically conductive layer of the separatorprovides an additional electronic path for active materials. In anembodiment, the electronically conductive layer is provided between saidinsulating layer and said positive electrode or said negative electrodeto provide an additional electronic path for the active materials. Insilicon or sulfur based electrodes the loss of electronic conductivityduring cycling significantly decreases the cell capacity and cycle life.In an embodiment, contact of the separated active material with theelectronically conductive separator creates an auxiliary currentcollector for the lost active material and improves the cycle efficiencyof the cell.

In a further embodiment, the electronically conductive layer is achemically reactive layer and a chemical reaction happens between theelectronically conductive layer and an electronical short (internal,such as a dendrite or a foreign metallic layer, or external) between thesaid electrically conductive layer of the said separator and saidpositive electrode or said negative electrode. In an embodiment thechemical reaction consumes and or dissipates energy. In an embodiment, achemical reaction takes place between the material of the electronicallyconductive layer and the dendrite material after the dendrite contactsthe layer of electronically conductive material.

In an embodiment, a multi-layer battery separator with at least oneconductive layer is used to prolong the cycle life and safetyenhancement of the cell. The conductive layer may have an external tabthat can be used for monitoring the cell or be used to “control” thecell. The conductive layer prolongs the cycle life of the battery by oneor more mechanisms. In the case with no auxiliary external tab: a) as afree standing physical barrier, stronger than conventional PP-PPseparators, which limits the size of a short to the size of the pores ofthe conductive layer (an example is a 0.007 mm stainless steel or copperperforated film) and b) as a chemical reactive material to the shortmaterial, such that the reaction between the conductive layer and theshort results in energy consumption and may stop or remove the short (anexample is a 0.007 mm aluminum film or a 0.001 mm aluminum coating onone side of a porous polymer film, such as microporous PP-PP). When anexternal tab electronically connects the conductive layer to outside ofthe cell additional mechanisms include using the external to c) monitorthe voltage between any of the electrodes and the conductive layer or d)apply a voltage or current between any of the electrodes and theconductive layer. Mechanism d) includes the mechanism of d1) burning theshort, d2) activating solid electrolyte and d3) activating alloying withdendrite and d4) releasing other substances in the cell.

In an embodiment, an electrochemical cell comprises a positiveelectrode; a negative electrode; one or more electrolytes positionedbetween said positive electrode and said negative electrode; said one ormore electrolytes capable of conducting ionic charge carriers; and acomposite separator comprising at least one electronically insulatinglayer and at least one electronically conductive layer; said separatorpositioned between said positive electrode and said negative electrodesuch that said ionic charge carriers are able to be transported betweensaid positive electrode and said negative electrode but not electroniccharge carriers; wherein the said electronically conductive layer of thesaid separator has an external tab that can be used to monitor theperformance of the cell by measuring the voltage or current. In anembodiment, sometimes the voltage doesn't change significantly but thecurrent does slightly, for example the current change is equal C/100rate or higher of the cell capacity, between the said tab and one of theelectrodes.

In an embodiment, an electrochemical cell comprises: a positiveelectrode; a negative electrode; one or more electrolytes positionedbetween said positive electrode and said negative electrode; said one ormore electrolytes capable of conducting ionic charge carriers; and acomposite separator comprising at least one electronically insulatinglayer and at least one electronically conductive layer; said separatorpositioned between said positive electrode and said negative electrodesuch that said ionic charge carriers are able to be transported betweensaid positive electrode and said negative electrode but not electroniccharge carriers; wherein in the said electronically conductive layer ofthe said separator has an external tab that can be used to modify theperformance of the cell by applying a voltage or current between thesaid tab and one of the electrodes. In some embodiment theelectronically conductive layer can have a source of active ions, forexample can have a coating of lithium metal on it or can itself be madeof lithium, in a lithium ion cells, which can be used to provide activeions to the cell, such as to compensate the ion loss or to make Li-ioncells with non-lithiated electrodes.

In an embodiment, an electrochemical cell comprises: a positiveelectrode; a negative electrode; one or more electrolytes positionedbetween said positive electrode and said negative electrode; said one ormore electrolytes capable of conducting ionic charge carriers; and atleast a composite solid electrolyte comprising at least anelectronically non-conductive layer, at least a porous layer ofelectronically conductive material and at least a group of solidelectrolyte fibers or particles filling the pores/holes of the porouslayer; said solid electrolyte positioned between said positive electrodeand said negative electrode such that said ionic charge carriers areable to be transported between said positive electrode and said negativeelectrode, but not electronic charge carriers. In an embodiment, theparticles can consist of known solid electrolyte, such as known polymeror ceramic solid electrolytes. In another embodiment, the particles mayhave a source of active ions, for example can be lithium metal, in alithium ion cells, which can be used to provide active ions to the cell,such as to compensate the ion loss or to make Li-ion cells withnon-lithiated electrodes. In another embodiment, the said electronicallyconductive layer of the said solid electrolyte may have an external tabthat can be used to modify the performance of the cell by applying avoltage or current between the said tab and one of the electrodes.

In an embodiment, the electronically conductive and chemically reactivelayer reacts with a dendrite growing from the negative electrode. In anembodiment, the material of the electronically conductive and chemicallyreactive layer forms an alloy with the dendrite material. In anembodiment where lithium dendrite structures form at the negativeelectrode, the electronically conductive and chemically reactive layercomprises at least one of Al, Ti, Ni, Fe, conductive carbon, Super-Pcarbon, carbon black, Kenjen, stainless steel, Sn or Si. When Li₊ is oneof the ionic charge carriers, the electrolyte may be nonaqueous. In anembodiment where zinc dendrite structures form at the negativeelectrode, the electronically conductive and chemically reactive layercomprises a metallic layer.

In a further embodiment, the electronically conductive and chemicallyreactive layer reacts with foreign material accumulated at the negativeelectrode. Foreign metallic materials which can occur in batteries andlead to internal defects include, but are not limited to Cu, Al, Fe,Stainless Steel, Mn, Ni or Co. The foreign materials can be introducedto the cell during the manufacturing or can be dissolvated materialsfrom a cathode active material or a current collector, due to overvoltage.

In an embodiment, ionic charge carriers in the system deposit orelectroplate on the electronically conductive layer once a dendrite oraccumulation of foreign material makes contact with the electronicallyconductive layer.

In a further embodiment, the electronically conductive layer isthermally conductive. In an embodiment, the thermal conductivity of thislayer allows the layer to dissipate heat and further reduce thelikelihood that thermal runaway will occur in the system. In the eventthat an electronical short between the positive and negative electrodesdoes occur, the electronically and thermally conductive layer can helpdissipate the heat generated. In an embodiment, in the event offormation of an electronical short between the said electronicallyconductive layer of the said separator and said positive electrode orsaid negative electrode, said electronically conductive layer transportsthe heat away from the short location and reduces the likelihood of hotspots or thermal runaway. In an embodiment, the electronically andthermally conductive layer dissipates heat from the reaction between thedendrite and the layer. In an embodiment, the electronically conductivelayer provides a substantially homogeneous thermal field within saidelectrochemical cell. In an embodiment, the electronically conductivelayer is characterized by a thermal conductivity greater than 75 W/(m·K)or selected over the range of 75 W/(m·K) to 500 W/(m·K). In anembodiment, the enhanced thermal conductivity of the cell interiordecreases the probability of hot spots which increases the cellperformance, safety and cycle life. It can further lessen theprobability of nonuniform plating of active or foreign ions on the anodeand can decrease the side reactions.

In an additional aspect, each of the electronically conductive layers ofthe composite separator comprises an external connection tab. Theexternal connection tab may also be referred to as an external tab. Inan embodiment, the electronically conductive layer comprising anexternal connection tab is used to monitor performance of the cell bymeasuring the voltage or current between the external connection tab andone of the electrodes. In another embodiment, the electronicallyconductive layer comprises an external connection tab that is used tomodify the performance of the cell by applying a voltage or currentbetween the external connection tab of the electronically conductivelayer and either the external connection tab of one of the electrodes orof an additional electronically conductive layer in the compositeseparator.

In an aspect, the said separator has one or two electronicallyconductive layers, which can be used with external tabs to modify theelectric field inside the cell, which can modify the performance of thecell. In one embodiments, the change of the electric field as a functionof time can act as an ionic pump to redistribute the ions in the celland prevent hot spots or dendrites.

In embodiments, the composite separator comprises a plurality ofelectronically conductive layers, such as 2, 3 or 4 independentconductive layers. In embodiments, the conductive layers have the sameelectric potential or have different electric potentials. Embodiments ofthis aspect include composite separators wherein the electronicallyconductive layers are provided in electrical contact (optionally inphysical contact) with each other and, alternatively, wherein theelectronically conductive layers are not provided in electrical contact.In an embodiment, the composite separator comprises a plurality ofelectronically conductive layers each independently having a selectedelectric potential. In an embodiment, the composite separator comprisesa plurality of electronically conductive layers characterized by one ormore selected potential differences between electronically conductivelayers, for example, a composite separator comprising a firstelectronically conductive layer having a first electric potential and asecond electronically conductive layer having a second electricpotential characterized by a selected difference in voltage. Methods andsystems of the invention may further comprise independently electricallybiasing one or more electronically conductive layers of the compositeseparator, for example, to establish an electric field within at least aportion of the electrochemical cell resulting in enhancedelectrochemical or electronic performance, such as the avoidance ormitigation of dendrite formation and/or enhanced cycling performanceand/or cycle life.

In an embodiment, the disclosure provides an electrochemical cell

-   -   comprising a positive electrode comprising a positive electrode        active material and a first current collector in electronic        communication with the positive electrode active material, the        first current collection further comprising a first external        connection tab;    -   a negative electrode comprising a negative electrode active        material and a second current collector in electronic        communication with the negative electrode active material, the        second current collector further comprising a second external        connection tab;    -   one or more electrolytes positioned between said positive        electrode and said negative electrode; said one or more        electrolytes being ionically conductive; and    -   a composite separator comprising at least one electronically        insulating layer and at least one electronically conductive        layer; said composite separator being positioned between said        positive electrode and said negative electrode and being        permeable to ionic charge carriers, but not electronically        conductive across the composite separator;    -   wherein said electronically conductive layer further comprises a        third external connection tab.

In an embodiment, the third external connection tab is not provided inelectronic contact with said positive electrode or said negativeelectrode except through an optional connection through an externalcircuit. In an embodiment, the disclosure further provides anelectrochemical system, the system comprising an electrochemical celland a source of current or voltage connected between the third externalconnection tab connected to the electronically conducting layer and anexternal connection tab connected to one of the positive or negativeelectrode. In an embodiment, the source of current or voltage is also acontroller of current or voltage.

In an aspect, the disclosure provides a method for detection of anelectronical short in an electrochemical cell, the method comprising thesteps of

-   -   a) providing said electrochemical cell comprising:        -   a positive electrode comprising a positive electrode active            material and a first current collector in electronic            communication with the positive electrode active material,            the first current collection further comprising a first            external connection tab;        -   a negative electrode comprising a negative electrode active            material and a second current collector in electronic            communication with the negative electrode active material,            the second current collector further comprising a second            external connection tab;        -   one or more electrolytes positioned between said positive            electrode and said negative electrode; said one or more            electrolytes being ionically conductive; and        -   a composite separator comprising an electronically            insulating layer and an electronically conductive layer;            said composite separator being positioned between said            positive electrode and said negative electrode and being            permeable to ionic charge carriers, but not electronically            conductive across the composite separator;        -   wherein said electronically conductive layer further            comprises a third external connection tab and is not            provided in electrical contact with said positive electrode            or said negative electrode in the absence of said            electronical short    -   b) monitoring the voltage or current of said electrochemical        cell, wherein said electrochemical cell undergoes an observable        change in voltage upon formation of an electronical short        between the electronically conductive layer and said positive        electrode or said negative electrode.

In an embodiment, the positive electrode comprises a positive electrodeactive material and a first current collector in electroniccommunication with the positive electrode active material, the firstcurrent collection further comprising a first external connection tab;the negative electrode comprises a negative electrode active materialand a second current collector in electronic communication with thenegative electrode active material, the second current collector furthercomprising a second external connection tab; one or more ionicallyconductive electrolytes positioned between said positive electrode andsaid negative electrode; and a composite separator comprising at leastone electronically insulating layer and at least one electronicallyconductive layer; said composite separator being positioned between saidpositive electrode and said negative electrode and being permeable toionic charge carriers, but not electronically conductive across thecomposite separator; wherein said electronically conductive layerfurther comprises a third external connection tab and is not provided inelectronic contact with said positive electrode or said negativeelectrode except through an external circuit. In an embodiment, thethird external connection tab is connected to an external connection tabof one of the positive or negative electrode through an external circuitand the voltage or current between the electronically conducting layerand the positive or negative electrode is monitored.

In a further aspect, the disclosure provides a method of reducingdendrite growth in an electrochemical cell; said method comprising thesteps of:

-   -   a) providing said electrochemical cell comprising: a positive        electrode; a negative electrode; one or more electrolytes        positioned between said positive electrode and said negative        electrode; said one or more ionically conductive electrolytes;        and a composite separator comprising an electronically        insulating layer and an electronically conductive layer; said        composite separator being positioned between said positive        electrode and said negative electrode and being permeable to        ionic charge carriers, but not electronically conductive across        the composite separator; and    -   b) charging said electrochemical cell, wherein said        electronically conductive layer undergoes deposition,        electrochemical plating or chemical reaction with a dendrite        structure formed during discharge between the electronically        conductive layer and said positive electrode, negative electrode        or both.

In an aspect, the disclosure provides a method of operating anelectrochemical cell, the method comprising the steps of:

-   -   a) providing said electrochemical cell comprising:        -   a positive electrode;        -   a negative electrode;        -   one or more electrolytes positioned between said positive            electrode and said negative electrode; said one or more            ionically conductive electrolytes; and        -   a composite separator comprising an electronically            insulating layer and an electronically conductive layer;            said separator positioned between said positive electrode            and said negative electrode such that said charge carriers            are able to be transported between said positive electrode            and said negative electrode;    -   b) charging, discharging or charging and discharging said        electrochemical cell.

In an aspect, the disclosure provides a method of operating anelectrochemical cell, the method comprising the steps of:

-   -   a) providing said electrochemical cell comprising:        -   a positive electrode;        -   a negative electrode;        -   one or more electrolytes positioned between said positive            electrode and said negative electrode; said one or more            ionically conductive electrolytes; and        -   a composite separator comprising an electronically            non-conductive layer, a porous or perforated layer of            electronically conductive material and a plurality of fibers            or particles located within the pores or holes of the layer            of electronically conductive material; said separator            positioned between said positive electrode and said negative            electrode such that said charge carriers are able to be            transported between said positive electrode and said            negative electrode;    -   b) charging, discharging or charging and discharging said        electrochemical cell        In an embodiment, said electronically conductive layer provides        a substantially homogeneous electric field adjacent to and        within said positive electrode, said negative electrode or both,        thereby providing uniform ion deposition into said positive        electrode, said negative electrode or both. FIGS. 2 and 4        schematically illustrate insertion of an electronically isolated        electronically conductive layer (4) between the positive and        negative electrodes. During charging, a surface charge develops        on the conductive layer.

In a further embodiment, the electrodes and the electronicallyconducting layer comprise external connection tabs and the methodfurther comprises the step of applying a voltage or current between theexternal connection tab and one of the electrodes. In embodiment, theapplied voltage or current for each step of cycling is constant voltageor current or varying with time such as a sinusoidal, pulse or stepwave. In an embodiments with the external tab for the conductive layer:the applied voltage or current can be fixed voltage or current or canvary with time, such as a sinusoidal, pulse or step voltage or currentvarying between different arbitrary values.

In embodiments, the application of a voltage or current between theelectrodes and the electrically conducting layer achieves a variety ofeffects. In an embodiment, a solid electrolyte incorporated in thecomposite separator is activated by application of a voltage may varyingbetween the charge-discharge voltages of the electrolyte. In anembodiment, the application of voltage between the electronicallyconductive layer and the electrode is used to redistribute activematerial which has deposited at locations other than the desiredelectrode; in this embodiment, the application of voltage between theelectronically conductive layer and the electrode can be used to “cleanup” the cell. As an example it is known that active electrode materialmay be lost when charged particles deposit in the separator, such aszinc or zinc oxide particles in Zinc batteries or polysulfide particlesin Li-ion batteries, which severely reduces the cell capacity and cyclelife, applying a voltage between the conductive layer and the anode inthis case, e.g., every 50 cycles, can deposit back the active materialsfrom the separator to the anode and can result in higher cycle life. Infurther embodiment a layer of electrolyte additive or modifier isattached to the electronically conductive layer and the application ofcurrent or voltage to between the electronically conductive layer andthe electrode is used to release electrolyte additive or modifier intothe electrolyte. An additional example is shorting the conductive layerwith the cathode that assists in oxygen evolution during charging inmetal air batteries.

In an embodiment, the conductive layer can be used for charging ordischarging, a specific example is shorting the conductive layer withthe cathode that assists in oxygen evolution during charging in metalair batteries. Applying a voltage other than zero between the conductiveelectrode and the cathode or the anode can result in activatingassisting materials, such as modifiers to decrease the cell temperatureand assist in thermal runaway prevention.

Electrochemical Cell.

In an embodiment, the electrochemical cell is a secondary (rechargeable)electrochemical cell. In another embodiment, the electrochemical cell isa primary electrochemical cell. In embodiments, the electrochemical cellis a primary battery, a secondary battery, a fuel cell or a flowbattery, a lithium battery, a lithium ion battery, a zinc anode-basedbattery, a nickel cathode-based battery, a semi-solid battery or alead-acid-based battery. In additional embodiments, the electrochemicalcell is a Li—S, Li-Air, Li—LiFePO₄, or Zn—Ni electrochemical cell. Infurther embodiments the cell is Mg based or Na based.

Negative Electrode

In an embodiment where the cell is a lithium ion cell, the activematerial of the negative electrode is lithium metal, a lithium alloy,silicon, a silicon alloy, silicon-graphite or graphite. In an embodimentwhere the cell is a zinc cell, the anode material is Zn metal, ZnO orZn—ZnO. In an embodiment, the negative electrode comprises an activematerial in electronic communication with a current collector. In anembodiment, the current collector comprises an external connection tab;in an embodiment the external connection tab is integral with thecurrent collector. In an embodiment, the current collector is anelectronically conductive material such as a metal.

Positive Electrode

In embodiments where the cell is a lithium ion cell, the active materialof the positive electrode is NMC (lithium nickel-manganese-cobaltoxide), sulfur, sulfur-carbon, carbon-air, LCO (lithium cobalt oxide,LiCoO₂) or LFP (lithium iron phosphate, LiFePO₄). In embodiments wherethe cell is a zinc battery, the cathode material is graphite, NiOOH, Ag,or AgO. In an embodiment, the positive electrode comprises an activematerial in electronic communication with a current collector. In anembodiment, the current collector comprises an external connection tab;in an embodiment the external connection tab is integral with thecurrent collector. In an embodiment, the current collector is anelectronically conductive material such as a metal.

Electrolyte

In embodiments, the electrolyte is a liquid electrolyte, gelelectrolyte, polymer electrolyte or ceramic electrolyte. In embodiments,the electrolyte is aqueous or nonaqueous. When the electrochemical cellis a lithium ion battery, the electrolyte is preferably nonaqueous. Inan embodiment, the electrolyte comprises one or more lithium saltsdissolved in a nonaqueous solvent.

Solid Electrolyte

In an embodiment, the solid electrolyte can be a free standing layer ora coating layer. In another embodiment, the solid electrolyte is in theform of particles or fibers filling the holes-pores of an electronicallyinsulating layer or the electronically conductive layer. In anembodiment, a layer is provided comprising at least a porous layer ofelectronically conductive material and at least a group of fibers orparticles filling the pores or holes of the porous layer. A variety ofsolid electrolytes are known to the art and include, but are not limitedto LISICON (Lithium super ionic conductor, Li_(2+2x)Zn_(1-x)GeO₄), PEO(polyethylene oxide), NASICON, and LIPON.

Insulator

In embodiments, the electronically insulating layer comprises a polymer,an oxide, a glass or a combination of these. In embodiments, theelectronically insulating is nonwoven or a woven. In an embodiment, theinsulating layer is polymeric such as microporous or nonwoven PE, PP,PVDF, polyester or polyimide. In a further embodiment the insulatinglayer is an oxide such as aluminum oxide. In an embodiment, saidelectronically insulating comprises a coating provided on at least oneside of said electronically conductive layer. As an example, an aluminumoxide layer is provided on an aluminum layer. In an embodiment, theelectronically insulating comprises one or more perforated or porouslayers each independently having a porosity greater than or equal to30%, from 30% to 80% or from 50% to 75%. In an embodiment, one or moreperforated or porous layers each independently have a thickness selectedover the range of 20 nm to 1 mm, 0.005 mm to 1 mm, from 1 μm to 500 μmor from 5 μm to 100 μm. In an embodiment, the separator comprises afirst insulating layer having a plurality of apertures arranged in afirst pattern and a second insulating layer having a plurality ofapertures arranged in a second pattern; wherein said second pattern hasan off-set alignment relative to said first pattern such that an overlapof said apertures of said first insulating layer and said apertures ofsaid second insulating layer along axes extending perpendicularly fromsaid first insulating layer to said second insulating layer is less thanor equal to 20% In an embodiment, there is no overlap of the apertures.

Electronically Conductive Layer

In embodiments, said electronically conductive layer comprises achemically resistant material, a heat resistant material, a mechanicallyresistant material or any combination of these. In an embodiment, theconductive layer comprises a metal, alloy, carbon or a conductivepolymer. In an embodiment, the electronically conductive layer comprisesa metal foil, a metallic thin film, an electronically conductivepolymer, a carbonaceous material or a composite material of any ofthese. In an embodiment, the metal or alloy is selected from Al, Cu, Ti,Ni, Fe, stainless steel, Sn, Si, Au, Pt, Ag, Mn, Pb and their alloys andZircalloy, Hastalloy, and superalloys. In an embodiment, theelectronically conductive layer comprises a metal selected from thegroup consisting of Al, Ti, Cu, stainless steel, Ni, Fe, or any alloysor composites thereof. In an embodiment, the carbonaceous material isselected from conductive carbon, super-P, carbon black and activatedcarbon. In an embodiment, the electronically conducting polymer isselected from the linear-backbone “polymer blacks” (polyacetylene,polypyrrole, and polyaniline) and their copolymers, poly(p-phenylenevinylene) (PPV) and its soluble derivatives and poly(3-alkylthiophenes.In an embodiment, the electronically conducting layer does not reactchemically or electrochemically with the electrolyte. In an embodiment,electronically conductive layer comprises a metal reactive with anactive material of the negative or positive electrode. In an embodiment,the electronically conductive layer comprises a metal selected from thegroup consisting of Al and Sn. In embodiments, the thickness of theelectronically conductive layer is greater than zero and less than 1 mm,greater than zero and less than 0.1 mm, from 0.001 mm to 1 mm, from0.005 mm to 1 mm, from 0.005 mm to 0.5 mm, from 0.01 mm to 0.1 mm, from0.075 mm to 0.2 mm or from of 25 nm to 0.5 mm. In an embodiment, thecomposite separator further comprises one or more additionalelectronically conductive layers.

In another embodiment, the electronically conductive layer or a coatingon the electronically conductive layer provides a source of active ions.For example, in a lithium ion cells the electronically conductive layermay have a coating of lithium metal on it or may be made of lithium. Ina further embodiment, the electronically conducting layer is porous orperforated and holes or pores in the electronically conducting layer areat least partially filled with particles or fibers comprising a sourceof active ions. The source of active ions is used to provide active ionsto the cell, such as to compensate the ion loss or to make Li-ion cellswith non-lithiated electrodes.

In a further embodiment, the electronically conducting layer is porousor perforated and holes or pores in the electronically conductive layerare at least partially filled by particles or fibers of an activematerial. Suitable active materials include, but are not limited to,traditional electrode active materials such as LiTiO₂, silicon orgraphite. In an embodiment, application of a voltage or current betweenthe electronically conducting layer and one of the electrodes results ingain and release of ions by the fibers or particles, such that ioniccharge carriers are able to be transported between said positiveelectrode and said negative electrode through the pores or holes of theelectronically conducting layer. For example, a pulse or sinusoidalvoltage between 1 and 2.5 V may be applied between a graphite anode anda layer comprising LiTiO2 fibers inside a copper matrix in a Li-ion cellwith a cathode such as air or sulfur.

In a further embodiment, the electronically conducting layer is porousor perforated and holes or pores in the electronically conductive layerare at least partially filled by particles or fibers of a redox shufflematerial. In an embodiment, the redox shuffle material can be activatedby application of a voltage or current between an external tab connectedto the electronically conducting layer and an external tab connected toan electrode or another electronically conducting layer.

Exemplary Composite Separator Configurations:

FIG. 3A shows an exemplary configuration of an electrochemical cellincluding a multilayer separator with an electronically conductive layer(4) sandwiched between two electronically insulating layers (3). Cathode(1), Anode (2), Separator (3), Perforated or Porous Conductive Layer(4). Thickness of separator (3) is less between cathode (1) andconductive layer (4) than between anode (2) and conductive layer (4).FIG. 3B shows an exemplary configuration of a system including anelectrochemical cell similar to that shown in FIG. 3A and devices (5)for monitoring or applying voltage or current. Cathode (1), Anode (2),Separator (3), Perforated or Porous Conductive Layer (4). A device (5)for monitoring or applying voltage or current is connected between thecathode and anode and also between the electronically conductive layer(4) and the cathode (1)

FIG. 4A. shows an exemplary configuration of an electrochemical cellincluding a multilayer separator with an electronically conductive layer(4) sandwiched between two electronically insulating layers (3). Cathode(1), Anode (2), Separator (3), Perforated or Porous Conductive Layer(4). Thickness of separator (3) is less between anode (2) and conductivelayer (4) than between cathode (1) and conductive layer (4). FIG. 4Bshows an exemplary configuration of a system including anelectrochemical cell with a central electronically conductive layer anddevices (5) for monitoring or applying voltage or current. Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layer (4). Adevice (5) for monitoring or applying voltage or current is connectedbetween the cathode and anode and also between the electronicallyconductive layer (4) and the anode (2)

FIG. 5A shows an exemplary configuration of an electrochemical cellincluding a multilayer separator with two electronically conductivelayers. Cathode (1), Anode (2), Separator (3), Perforated or PorousConductive Layers (4). FIG. 5B shows an exemplary configuration of asystem including an electrochemical cell with two electronicallyconductive layers and devices (5) for monitoring or applying voltage orcurrent. Cathode (1), Anode (2), Separator (3), Perforated or PorousConductive Layer (4). A device (5) for monitoring or applying voltage orcurrent is connected between the cathode and anode and also between thetwo electronically conductive layers (4). FIG. 5C shows an exemplaryconfiguration of a system including an electrochemical cell with twoelectronically conductive layers and devices (5) for monitoring orapplying voltage or current. Cathode (1), Anode (2), Separator (3),Perforated or Porous Conductive Layer (4). A device (5) for monitoringor applying voltage or current is connected between the cathode andanode and also between one electronically conductive layer (4) and thecathode (1) and between the other electronically conductive layer (4)and the anode (2).

FIG. 6 shows an exemplary configuration of an electrochemical cellincluding a multilayer separator with two electronically conductivelayers. One electronically conductive layer is in contact with thecathode (1) while the other is located between two separator layers (3).Cathode (1), Anode (2), Separator (3), Perforated or Porous ConductiveLayers (4).

FIG. 7 shows an exemplary configuration of a multilayer separator withtwo electronically conductive layers. One electronically conductivelayer is in contact with the anode (e) while the other is locatedbetween two separator layers (3). Cathode (1), Anode (2), Separator (3),Perforated or Porous Conductive Layers (4).

In an aspect, the invention provides an electrochemical cell comprising:(I) a positive electrode; (ii) a negative electrode; (ii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iii) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein thepresence of the said electronically conductive layer(s) of the saidseparator affects the performance of the electrochemical cellperformance upon formation of an electronical short between any of thesaid electrodes or the said electronically conductive layer.

In a further aspect, the invention provides an electrochemical cellcomprising: (i) a positive electrode; (ii) a negative electrode; (ii)one or more electrolytes positioned between said positive electrode andsaid negative electrode; said one or more electrolytes capable ofconducting ionic charge carriers; and (iii) a composite separatorcomprising at least one electronically insulator layer and at least oneelectronically conductive layer; said separator positioned between saidpositive electrode and said negative electrode such that said ioniccharge carriers are able to be transported between said positiveelectrode and said negative electrode but not electronic chargecarriers; wherein each said electronically conductive layer of the saidseparator further comprises an external connection tab and the cellfurther comprises a voltage or current applying circuit connectedbetween each of said electrochemically conductive layers and one of thepositive or the negative electrode, thereby allowing modification of theelectric field and the performance of the electrochemical cell. In anembodiment, each said electronically conductive layer is a coatingprovided on at least a portion of said electronically insulating layer.In an embodiment, there are two electronically conductive layers andthree electronically insulating layers, each electronically conductivelayer being separated from the other and the positive and negativeelectrodes by an electronically insulating layer.

In an aspect, the invention provides an electrochemical cell comprising:(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein inthe event of formation of an electrical short between the saidelectrically conductive layer of the said separator and said positiveelectrode or said negative electrode, chemical reaction happens betweenthe electronically conductive layer and electronic short (internal, suchas a dendrite or a foreign metallic layer, or external); which consumesand or dissipates energy.

In an aspect, the invention provides an electrochemical cell comprising:(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein inthe event of formation of an electronically short between the saidelectronically conductive layer of the said separator and said positiveelectrode or said negative electrode, the said electronically conductivelayer transports the heat away from the short location and reduces thelikelihood of hot spots or thermal runaway

In an aspect, the invention provides an electrochemical cell comprising:(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein inthe said electronically conductive layer of the said separator has anexternal tab that can be used to monitor the performance of the cell bymeasuring the voltage or current. Optionally, sometimes the voltagedoesn't change but the current does slightly, say the current=C/100 rateor higher of the cell capacity) between the said tab and one of theelectrodes.

In an aspect, the invention provides an electrochemical cell comprising(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein inthe said electronically conductive layer of the said separator has anexternal tab that can be used to modify the performance of the cell byapplying a voltage or current between the said tab and one of theelectrodes. Optionally, the electronically conductive layer can have asource of active ions, for example can have a coating of lithium metalon it or can itself be made of lithium, in a lithium ion cells, whichcan be used to provide active ions to the cell, such as to compensatethe ion loss or to make li-ion cells with non-lithiated electrodes)

In an aspect, the invention provides an electrochemical cell comprising(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) at least a composite solid electrolytecomprising at least an electronically non-conductive layer, at least aporous layer of electronically conductive material and at least a groupof solid electrolyte fibers or particles filling the pores/holes of theporous layer; said solid electrolyte positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode, but not electronic charge carriers; Optionally,the particles can consist of known solid electrolyte, such as knownpolymer or ceramic solid electrolytes. Optionally, the particles mayhave a source of active ions, for example can be lithium metal, in alithium ion cells, which can be used to provide active ions to the cell,such as to compensate the ion loss or to make li-ion cells withnon-lithiated electrodes). Optionally, the said electronicallyconductive layer of the said solid electrolyte may have an external tabthat can be used to modify the performance of the cell by applying avoltage or current between the said tab and one of the electrodes.

In an aspect, the invention provides a composite solid electrolyte foran electrochemical cell comprising at least an electronicallynon-conductive layer, at least a porous layer of electronicallyconductive material and at least a group of fibers or particles fillingthe pores/holes of the porous layer; wherein in the said electronicallyconductive layer of the said solid electrolyte has an external tab forchanging the voltage between the particles and the electrodes byapplying a voltage or current between the said tab and one of theelectrodes; where in the applied voltage or current between the betweenthe said embedded particles and the electrodes results in the gainingand releasing the ions by the fibers/particles, such that said ioniccharge carriers are able to be transported between said positiveelectrode and said negative electrode, but not electronic chargecarriers, through the solid electrolyte. Optionally, the solid particlescan be a component of the electronically conductive layer, but: Thesolid particles can be a free standing layer or a coating layer; or thesolid particles can be a component of the electronically non-conductivelayer, e.g., particles or fibers filling the holes-pores of theelectronically non-conductive layer. Optionally, the solid particles canbe traditional electrode active material (transporting ions withappropriate voltage or current, such as LiTiO2, Silicon or Graphite).Optionally, the applied voltage or current for each step of cycling canbe constant voltage or current or a time variable such as a sinusoidal,pulse or step wave varying between the charge-discharge voltages of thenontraditional solid electrolyte.) Optionally, a pulse or sinusoidalbetween 1 and 2.5V applied between a graphite anode and the compositesolid electrolyte (LiTiO2 fibers inside a copper matrix) in a li-ioncell, for example with an air or sulfur electrode.

In an aspect, the invention provides an electrochemical cell comprising:(I) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) at least a composite solid electrolytecomprising at least an electronically non-conductive layer, at least aporous layer of electronically conductive material and at least a groupof fibers or particles filling the pores/holes of the porous layer; saidcomposite solid electrolyte positioned between said positive electrodeand said negative electrode such that said ionic charge carriers areable to be transported between said positive electrode and said negativeelectrode, but not electronic charge carriers; wherein in the saidelectronically conductive layer of the said separator has an externaltab that can be used to modify the performance of the cell by applying avoltage or current between the said tab and one of the electrodes.

In an aspect, the invention provides an electrochemical cell comprising:(i) a positive electrode; (ii) a negative electrode; (iii) one or moreelectrolytes positioned between said positive electrode and saidnegative electrode; said one or more electrolytes capable of conductingionic charge carriers; and (iv) a composite separator comprising atleast one electronically insulator layer and at least one electronicallyconductive layer; said separator positioned between said positiveelectrode and said negative electrode such that said ionic chargecarriers are able to be transported between said positive electrode andsaid negative electrode but not electronic charge carriers; wherein saidelectronically conductive layer(s) of the said separator changes theelectrochemical cell performance upon formation of an electrical shortbetween the electrically conductive layer and said positive electrode orsaid negative electrode

The conductive layer can be used for charging or discharging, a specificexample is shorting the conductive layer with the cathode that assistsin oxygen evolution during charging in metal air batteries. Applying avoltage other than zero between the conductive electrode and the cathodeor the anode can result in activating assisting materials, such asmodifiers to decrease the cell temperature and thermal runawayprevention.

As an another example it is known that active electrode material may belost when charged particles deposit in the separator, such as zinc orzinc oxide particles in Zinc batteries or polysulfide particles inli-ion batteries, which severely reduces the cell capacity and cyclelife, applying a voltage between the conductive layer and the anode inthis case, e.g., every 50 cycles, can deposit back the active materialsfrom the separator to the anode and can result in higher cycle life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Electroplating (charging) without the conductive layer. Thecircles are the positive ions leaving the opposite electrode anddepositing on the electrode of interest.

FIG. 2. Electroplating (charging) with the conductive layer (4) in themiddle.

FIG. 3A. Exemplary configuration of an electrochemical cell including amultilayer separator with a central electronically conductive layer.Cathode (1), Anode (2), Separator (3), Perforated or Porous ConductiveLayer (4). Thickness of separator (3) is less between cathode (1) andconductive layer (4) than between anode (2) and conductive layer (4).

FIG. 3B. Exemplary configuration of a system including anelectrochemical cell with a central electronically conductive layer anddevices (5) for monitoring or applying voltage or current. Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layer (4). Adevice (5) for monitoring or applying voltage or current is connectedbetween the cathode and anode and also between the electronicallyconductive layer (4) and the cathode (1).

FIG. 4A. Exemplary configuration of an electrochemical cell including amultilayer separator with a central electronically conductive layer.Cathode (1), Anode (2), Separator (3), Perforated or Porous ConductiveLayer (4). Thickness of separator (3) is less between anode (2) andconductive layer (4) than between cathode (1) and conductive layer (4).

FIG. 4B. Exemplary configuration of a system including anelectrochemical cell with a central electronically conductive layer anddevices (5) for monitoring or applying voltage or current. Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layer (4). Adevice (5) for monitoring or applying voltage or current is connectedbetween the cathode and anode and also between the electronicallyconductive layer (4) and the anode (2).

FIG. 5A. Exemplary configuration of an electrochemical cell including amultilayer separator with two central electronically conductive layers.Cathode (1), Anode (2), Separator (3), Perforated or Porous ConductiveLayers (4).

FIG. 5B. Exemplary configuration of a system including anelectrochemical cell with two electronically conductive layers anddevices (5) for monitoring or applying voltage or current. Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layer (4). Adevice (5) for monitoring or applying voltage or current is connectedbetween the cathode and anode and also between the two electronicallyconductive layers (4).

FIG. 5C. Exemplary configuration of a system including anelectrochemical cell with two electronically conductive layers anddevices (5) for monitoring or applying voltage or current. Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layer (4). Adevice (5) for monitoring or applying voltage or current is connectedbetween the cathode and anode and also between one electronicallyconductive layer (4) and the cathode (1) and between the otherelectronically conductive layer (4) and the anode (2).

FIG. 6. Exemplary configuration of an electrochemical cell including amultilayer separator with two electronically conductive layers. Oneelectronically conductive layer is in contact with the cathode (1) whilethe other is located between two separator layers (3). Cathode (1),Anode (2), Separator (3), Perforated or Porous Conductive Layers (4).

FIG. 7. Exemplary configuration of a multilayer separator with twoelectronically conductive layers. One electronically conductive layer isin contact with the anode (2) while the other is located between twoseparator layers (3). Cathode (1), Anode (2), Separator (3), Perforatedor Porous Conductive Layers (4).

FIG. 8. Capacity (mAh) versus cycles for a LiTiO₂, Toray, Al, lithiumcell.

FIG. 9. Capacity (mAh) versus cycles for a LiTiO₂, Celgard, Cu, lithiumcell.

FIG. 10 Capacity (mAh) versus cycles for a LiTiO₂, Celgard, Ni, lithiumcell.

FIG. 11. Capacity (mAh) versus cycles for a pouch cell containing EC:EMC (3:7 wt %)-1.2M LiPF₆, Toda NMC(111) vs. Li. Cathode active wt:0.2021 g. Specific capacity at 12 mA discharge=148 mAh/g.

FIG. 12. Ionic diodes, in the form of a pair of one directional ionchannels with opposite directions, as components of the separator and/orelectrolyte.

FIG. 13. Porous metal structure Anode.

FIG. 14. Schematic illustration of a battery before use. All of theelectrode particles are electronically connected.

FIG. 15. Schematic illustration of the battery after charging, theelectrode particles have a large shape change

FIG. 16. Schematic illustration of the battery, with the conventionalseparator, after several cycling, some of the electrode particles havelost their electronic connection with the current collector and thus arein-active.

FIG. 17. Schematic illustration of the battery, with the new separator,after several cycling, some of the electrode particles have lost theirconventional electronic connection with the current collector but thenew separator provides a new path for some of the electrode particles.Green shows the new path of the electrons, due to the new separator.

FIG. 18. Example showing combinations of the multi-layer separatorsbetween anode and cathode electrodes

DETAILED DESCRIPTION OF THE INVENTION

In general the terms and phrases used herein have their art-recognizedmeaning, which can be found by reference to standard texts, journalreferences and contexts known to those skilled in the art. The followingdefinitions are provided to clarify their specific use in the context ofthe invention.

Referring to the drawings, like numerals indicate like elements and thesame number appearing in more than one drawing refers to the sameelement. In addition, hereinafter, the following definitions apply:

The term “electrochemical cell” refers to devices and/or devicecomponents that convert chemical energy into electrical energy orelectrical energy into chemical energy. Electrochemical cells have twoor more electrodes (e.g., positive and negative electrodes) and anelectrolyte, wherein electrode reactions occurring at the electrodesurfaces result in charge transfer processes. Electrochemical cellsinclude, but are not limited to, primary batteries, secondary batteriesand electrolysis systems. In certain embodiments, the termelectrochemical cell includes fuel cells, supercapacitors, capacitors,flow batteries, metal-air batteries and semi-solid batteries. Generalcell and/or battery construction is known in the art, see e.g., U.S.Pat. Nos. 6,489,055, 4,052,539, 6,306,540, Seel and Dahn J. Electrochem.Soc. 147(3) 892-898 (2000).

The term “capacity” is a characteristic of an electrochemical cell thatrefers to the total amount of electrical charge an electrochemical cell,such as a battery, is able to hold. Capacity is typically expressed inunits of ampere-hours. The term “specific capacity” refers to thecapacity output of an electrochemical cell, such as a battery, per unitweight. Specific capacity is typically expressed in units ofampere-hours kg⁻¹.

The term “discharge rate” refers to the current at which anelectrochemical cell is discharged. Discharge rate can be expressed inunits of ampere. Alternatively, discharge rate can be normalized to therated capacity of the electrochemical cell, and expressed as C/(X t),wherein C is the capacity of the electrochemical cell, X is a variableand t is a specified unit of time, as used herein, equal to 1 hour.

“Current density” refers to the current flowing per unit electrode area.

Electrode refers to an electrical conductor where ions and electrons areexchanged with electrolyte and an outer circuit. “Positive electrode”and “cathode” are used synonymously in the present description and referto the electrode having the higher electrode potential in anelectrochemical cell (i.e. higher than the negative electrode).“Negative electrode” and “anode” are used synonymously in the presentdescription and refer to the electrode having the lower electrodepotential in an electrochemical cell (i.e. lower than the positiveelectrode). Cathodic reduction refers to a gain of electron(s) of achemical species, and anodic oxidation refers to the loss of electron(s)of a chemical species. Positive electrodes and negative electrodes ofthe present electrochemical cell may further comprise a conductivediluent, such as acetylene black, carbon black, powdered graphite, coke,carbon fiber, graphene, and metallic powder, and/or may furthercomprises a binder, such as a polymer binder. Useful binders forpositive electrodes in some embodiments comprise a fluoropolymer such aspolyvinylidene fluoride (PVDF). Positive and negative electrodes of thepresent invention may be provided in a range of useful configurationsand form factors as known in the art of electrochemistry and batteryscience, including thin electrode designs, such as thin film electrodeconfigurations. Electrodes are manufactured as disclosed herein and asknown in the art, including as disclosed in, for example, U.S. Pat. Nos.4,052,539, 6,306,540, and 6,852,446. For some embodiments, the electrodeis typically fabricated by depositing a slurry of the electrodematerial, an electronically conductive inert material, the binder, and aliquid carrier on the electrode current collector, and then evaporatingthe carrier to leave a coherent mass in electrical contact with thecurrent collector.

“Electrode potential” refers to a voltage, usually measured against areference electrode, due to the presence within or in contact with theelectrode of chemical species at different oxidation (valence) states.

“Electrolyte” refers to an ionic conductor which can be in the solidstate, the liquid state (most common) or more rarely a gas (e.g.,plasma).

“Standard electrode potential”) (E° refers to the electrode potentialwhen concentrations of solutes are 1M, the gas pressures are 1 atm andthe temperature is 25 degrees Celsius. As used herein standard electrodepotentials are measured relative to a standard hydrogen electrode.

“Active material” refers to the material in an electrode that takes partin electrochemical reactions which store and/or deliver energy in anelectrochemical cell.

“Cation” refers to a positively charged ion, and “anion” refers to anegatively charged ion.

“Electrical contact,” “electrical communication”, “electronic contact”and “electronic communication” refer to the arrangement of one or moreobjects such that an electric current efficiently flows from one objectto another. For example, in some embodiments, two objects having anelectrical resistance between them less than 100Ω are considered inelectrical communication with one another. An electrical contact canalso refer to a component of a device or object used for establishingelectrical communication with external devices or circuits, for examplean electrical interconnection. “Electrical communication” also refers tothe ability of two or more materials and/or structures that are capableof transferring charge between them, such as in the form of the transferof electrons. In some embodiments, components in electricalcommunication are in direct electrical communication wherein anelectronic signal or charge carrier is directly transferred from onecomponent to another. In some embodiments, components in electricalcommunication are in indirect electrical communication wherein anelectronic signal or charge carrier is indirectly transferred from onecomponent to another via one or more intermediate structures, such ascircuit elements, separating the components.

A short in a battery refers to electronic connection between twoelectronically conductive layers with different charges (such as twoelectrodes), which can be internal (dendrite or foreign materials) orexternal (e.g., a wire between two opposite tabs). The term“electronical short” or “electric short” may also be used in place of“short”.

“Electrical conductivity” or “electrically conductive” refers totransfer of charges which can be ionic (ions) or electronic (electrons).“Electronic conductivity” or “electronically conductive” refers totransfer of charges which are electronic (electrons). As used herein, aseparator element can permit passage of ions through pores orperforations present in element even though the material of theseparator element is not ionically conductive. Such an element may bereferred to as having low electronic resistance. As an example aperforated copper sheet can be ionically conductive as well aselectronically conductive. “Ionic conductivity” or “ionicallyconductive” refers to transport of ionic charge carriers.

“Thermal contact” and “thermal communication” are used synonymously andrefer to an orientation or position of elements or materials, such as acurrent collector or heat transfer rod and a heat sink or a heat source,such that there is more efficient transfer of heat between the twoelements than if they were thermally isolated or thermally insulated.Elements or materials may be considered in thermal communication orcontact if heat is transported between them more quickly than if theywere thermally isolated or thermally insulated. Two elements in thermalcommunication or contact may reach thermal equilibrium or thermal steadystate and in some embodiments may be considered to be constantly atthermal equilibrium or thermal steady state with one another. In someembodiments, elements in thermal communication with one another areseparated from each other by a thermally conductive material orintermediate thermally conductive material or device component. In someembodiments, elements in thermal communication with one another areseparated by a distance of 1 μm or less. In some embodiments, elementsin thermal communication with one another are provided in physicalcontact.

“High mechanical strength” refers to a property of components ofseparator systems of the invention, such as first, second, third andfourth high mechanical strength layers, having a mechanical strengthsufficient to prevent physical contact of opposite electrodes,sufficient to prevent short circuiting due to external objects withinthe cell, such as metallic particles from fabrication, and sufficient toprevent short circuiting due to growth of dendrites between positive andnegative electrodes of an electrochemical cell, for example, duringcharge and discharge cycles of a secondary electrochemical cell. In anembodiment, for example, a high mechanical strength layer has amechanical strength sufficient to prevent piercing due to externalobjects in the cell, such as metallic particles from the fabrication,and shorts due to the growth of dendrites between electrodes. In anembodiment, for example, a high mechanical strength layer has amechanical strength sufficient to prevent shorting between the positiveelectrode and the negative electrode of an electrochemical cell due toexternal objects in the cell such as metallic particles from thefabrication and shorts due to the growth of dendrites betweenelectrodes. In an embodiment, for example, a high mechanical strengthlayer is characterized by a Young's modulus greater than or equal to 500MPa, and optionally for some applications a Young's modulus greater thanor equal to 1 GPa, and optionally for some applications a Young'smodulus greater than or equal to 10 GPa, and optionally for someapplications a Young's modulus greater than or equal to 100 GPa. In anembodiment, for example, a high mechanical strength layer ischaracterized by a yield strength greater than or equal to 5 MPa, andoptionally for some applications a yield strength greater than or equalto 50 MPa, and optionally for some applications a yield strength greaterthan or equal to 100 MPa, and optionally for some applications a yieldstrength greater than or equal to 500 MPa. In an embodiment, forexample, a high mechanical strength layer is characterized by apropagating tear strength greater than or equal to 0.005 N, andoptionally for some applications a propagating tear strength greaterthan or equal to 0.05 N, a propagating tear strength greater than orequal to 0.5 N, a propagating tear strength greater than or equal to 1N. In an embodiment, for example, a high mechanical strength layer ischaracterized by an initiating tear strength greater than or equal to 10N, and optionally for some applications an initiating tear strengthgreater than or equal to 100 N. In an embodiment, for example, a highmechanical strength layer is characterized by a tensile strength greaterthan or equal to 50 MPa, and optionally for some applications a tensilestrength greater than or equal to 100 MPa, and optionally for someapplications a tensile strength greater than or equal to 500 MPa, andoptionally for some applications a tensile strength greater than orequal to 1 GPa. In an embodiment, for example, a high mechanicalstrength layer is characterized by an impact strength greater than orequal to 10 N cm, and optionally for some applications to an impactstrength greater than or equal to 50 N cm, and optionally for someapplications to an impact strength greater than or equal to 100 N cm,and optionally for some applications to an impact strength greater thanor equal to 500 N cm.

“Chemically resistant” refers a property of components, such as layers,of separators and electrochemical systems of the invention wherein thereis no significant chemical or electrochemical reactions with the cellactive materials, such as electrodes and electrolytes. In certainembodiments, chemically resistant also refers to a property wherein thetensile retention and elongation retention is at least 90% in theworking environment of an electrochemical system, such as anelectrochemical cell.

“Thermally stable” refers a property of components, such as layers, ofseparators and electrochemical systems of the invention wherein there isno significant chemical or electrochemical reactions due to normal andoperational thermal behavior of the cell. In certain embodiments,thermally stable also refers to materials wherein the melting point ismore than 100 Celsius, and preferably for some embodiments more than 300Celsius, and optionally the coefficient of thermal expansion is lessthan 50 ppm/Celsius. In an embodiment, thermally stable refers to aproperty of a component of the separator system such that it may performin a rechargeable electrochemical cell without undergoing a change sizeor shape with the temperature that significantly degrades theperformance of the electrochemical cell.

“Porosity” refers to the amount of a material or component, such as ahigh mechanical strength layer, that corresponds to pores, such asapertures, channels, voids, etc. Porosity may be expressed as thepercentage of the volume of a material, structure or device component,such as a high mechanical strength layer, that corresponds to pores,such as apertures, channels, voids, etc., relative to the total volumeoccupied by the material, structure or device component.

In an aspect, the disclosure provides a multi-layer battery separatorwith at least one conductive layer to prolong the cycle life and safetyenhancement of the cell. The conductive layer may have an external tabthat can be used for monitoring the cell or be used to “control” thecell. The conductive layer prolongs the cycle life of the battery bydifferent mechanisms. In the case where the conductive layer does notinclude an auxiliary external tab the conductive layer may prolong bycycle life by one or all of the following mechanisms: a) as a freestanding physical barrier, stronger than conventional PP-PP separators,which limits the size of a short to the size of the pores of theconductive layer (an example is a 0.007 mm thick stainless steel orcopper perforated film) and b) as a chemically reactive material to theshort material, such that the reaction between the conductive layer andthe short results in energy consumption and may stop or remove the short(an example is a 0.007 mm aluminum film or a 0.001 mm aluminum coatingon one side of a porous polymer film, such as microporous PP-PP). Whenan external tab electronically connects the conductive layer to outsideof the cell additional mechanisms include c) use of the external tab tomonitor the voltage between any of the electrodes and the conductivelayer and d) use of the external tab to apply a voltage or currentbetween any of the electrodes and the conductive layer. Mechanism d)includes the mechanisms of d1) burning the short, d2) activating a solidelectrolyte, d3) activating alloying with dendrite and d4) releasingother substances in the cell.

In an embodiment, for example, the composite separator is provided inphysical contact with the positive electrode and the negative electrode.In an embodiment, for example, the separator system with an electrolytean ionic conductivity between the positive electrode and the negativeelectrode equal to or greater than 1×10⁻³ S/cm, optionally for someapplications preferably greater than 1×10⁻² S/cm. In an embodiment, forexample, the separator system in the presence of an appropriateelectrolyte provides a net ionic resistance from the positive electrodeto the negative electrode selected over the range of 0.5 ohm cm² to 25ohm cm², and preferably for some applications less than 5 ohm cm².

In an embodiment, for example, a layer permeable to ionic chargecarriers has an ionic resistance less than or equal to 20 ohm-cm², andpreferably for some embodiments less than or equal to 2 ohm-cm², andpreferably for some embodiments less than or equal to 1 ohm-cm².

Optionally, an ionically conductive and electronically insulatingmaterial has an ionic conductivity greater than or equal to 10⁻⁵ S/cm,greater than or equal to 10⁻⁴ S/cm, greater than or equal to 10⁻⁴ S/cm,greater than or equal to 10⁻³ S/cm, greater than or equal to 10⁻² S/cm,greater than or equal to 10⁻¹ S/cm, greater than or equal to 10 S/cm,selected from the range of 10⁻⁷ S/cm to 100 S/cm, selected from therange of 10⁻⁵ S/cm to 10 S/cm, selected from the range of 10⁻³ S/cm to 1S/cm. Optionally, the first ionically conductive and electronicallyinsulating material has an ionic conductivity selected from the range of10⁻⁷ S/cm to 100 S/cm at an operating temperature of the cell.

In an embodiment, the electronically conductive separator has a thermalconductivity greater than or equal to 5 W·m⁻¹·K⁻¹, greater than or equalto 10 W·m⁻¹·K⁻¹, greater than or equal to 20 W·m⁻¹·K⁻¹, greater than orequal to 50 W·m⁻¹·K⁻¹, greater than or equal to 100 W·m⁻¹·K⁻¹ or greaterthan or equal to 200 W·m⁻¹·K⁻¹. In an embodiment, the thermalconductivity is from 50 W·m⁻¹·K¹ to 500 W·m⁻¹·K⁻¹. or 100 W·m⁻¹·K⁻¹ to500 W·m⁻¹·K⁻¹, as measured at 25° C.

In embodiments, the layer permeable to ionic charge carriers is selectedfrom the group consisting of a perforated polymer separator, a porouspolymer separator, a perforated ceramic separator, a porous ceramicseparator, a perforated glass separator, a porous glass separator, aperforated metal or perforated alloy separator, a porous metal or porousalloy separator, a metal mesh and an alloy mesh. In an embodiment, forexample, a layer permeable to ionic charge carriers is selected from thegroup consisting of a ceramic electrolyte, a glass electrolyte, apolymer electrolyte or another solid electrolyte. In an embodiment, forexample, the layer permeable to ionic charge carriers comprises a glasselectrolyte, such as Nafion or ZrO₂ or NASICON or LISICON or LIPON, or apolymer electrolyte such as PEO.

Optionally, the first ionically conductive and electronically insulatingmaterial comprises a solid electrolyte, a gel electrolyte, a polymerelectrolyte, LISICON, NASICON, PEO, Li₁₀GeP₂S₁₂, LIPON, PVDF, Li₃N,Li₃P, LiI, LiBr, LiCl, LiF, oxide perovskite, La_(0.5), Li_(0.5)TiO₃,thio-LISICON, Li_(3.25)Ge_(0.25)P_(0.75)S₄, glass ceramics, Li₇P₃S₁₁,glassy materials, Li₂S—SiS₂—Li₃PO₄, lithium nitride, polyethylene oxide,Doped Li₃N, Li₂S—SiS₂—Li₃PO₄, LIPON, Li₁₄Zn(GeO₄)₄, Li-beta-alumina,Li_(3.6)Si_(0.6)P_(0.4)O₄, Li₂S—P₂S₅, PEO-LiClO₄,LiN(CF₃SO₂)₂/(CH₂CH₂O)₈, NaPON, ZrO₂, Nation, PEDOT:PSS, SiO₂, PVC,glass fiber mat, alumina, silica glass, ceramics, glass-ceramics,water-stable polymers, glassy metal ion conductors, amorphous metal ionconductors, ceramic active metal ion conductors, glass-ceramic activemetal ion conductors, an ion conducting ceramic, an ion conducting solidsolution, an ion conducting glass, a solid lithium ion conductor or anycombination of these

Optionally, the above-mentioned first ionically conductive andelectronically insulating material has an average porosity less than 1%.Preferably, the first ionically conductive and electronically insulatingmaterial is non-porous. Optionally, the first ionically conductive andelectronically insulating material has an average porosity selected fromthe range of 0% to 5%. Optionally, the first ionically conductive andelectronically insulating material is substantially free of pinholes,cracks, holes or any combination of these. Optionally, the firstionically conductive and electronically insulating material issubstantially free of defects. Optionally, the first ionicallyconductive and electronically insulating material is doped.

In an embodiment, the electronically insulating layers and theelectronically conducting layers each independently have an averagethickness selected over the range 25 nm to 1 mm, optionally for someapplications selected over the range 25 nm to 15 μm, and optionally forsome applications selected over the range of 1 μm to 100 μm, andoptionally for some applications selected over the range of 5 μm to 1mm. In an embodiment, for example, any of, and optionally all of,electronically insulating layers and the electronically conductinglayers each independently have an average thickness selected over therange 10 nm to 2 μm or selected over the range 2 μm to 50 μm.

This invention is further explained with the following embodiments,which are not intended to limit the scope of this invention.

Example 1 Multilayer Separators Made of Materials that Upon ElectronicContact with an Electrode Result in an Observable Change in Voltage

The electrochemical cells in this disclosure include, but are notlimited to, batteries, fuel cells, flow batteries and semi-solidbatteries. Any of the electrode active materials can be solid, liquid,gas, flowable semi-solid or condensed liquid composition. A flowableanodic semi-solid (also referred to herein as “anolyte”) and/or aflowable cathodic semi-solid (also referred to herein as “catholyte”)are/is comprised of a suspension of electrochemically-active agents(anode particulates and/or cathode particulates) and, optionally,electronically conductive particles (e.g., carbon). The cathodicparticles and conductive particles are co-suspended in an electrolyte toproduce a catholyte semi-solid. The anodic particles and conductiveparticles are co-suspended in an electrolyte to produce an anolytesemi-solid. All voltages are wrt Li₊/Li.

Safer Batteries:

Overvoltage protection and Safe-short separators and electrochemicalcells implementing them: multilayer separators made of materials thatupon electronic contact with an electrode result in an observable changein the voltage. An electronic short between the opposite electrodes canbe very dangerous, the suggested separators can not only give an earlywarning to the user before any catastrophic failure but can also reducethe severity of a battery failure. An example is an electrochemical cellwith multilayer separators such that at least one of the separatorlayers is made of a metal (e.g. aluminum, titanium, copper, stainlesssteel, nickel, iron) or alloy or an electronically conductive materialsuch as electronically conductive polymers for example such that theshort can results in ion deposition on at least a part of the saidseparator. The said layer(s) can be porous or perforated to allow thepassage of ions with the assistance of any electrolytes. The saidseparator can further have electronically insulating layers or coatingssuch that there is no electronic connection between the oppositeelectrodes inside the cell when separated with the said separator. Anyinternal electronic connection between the opposite electrodes e.g., dueto external or internal objects (such as formed dendrites or initialdefects from manufacturing) thus may reach the internal electronicallyconductive layer(s) which results in change of voltage and can furtherprevent the short between the opposite electrodes. As an example in a3.7V lithium battery such as with lithium metal anode, LiCoO₂ cathodeand non-aqueous electrolyte, implementing a separator which has aluminumas one of the components such as perforated aluminum foil, a shortbetween the lithium metal and the aluminum due to dendrite formation,external metallic objects or high temperature inside the cell willchange the voltage of the cell, further the dendrite can chemicallyprefer to stop growth as an electronic contact between the aluminum andlithium dendrite can change the electrochemical reactions. This is inaddition to the benefit due to mechanically strong aluminum layer thatmay prevent the shorts or stop the dendrite. The excellent electronicand thermal conductivity of the metallic membrane can even affect thecell electrical and thermal fields such that the nucleation and growthof the dendrites is slowed down or stopped. All of these may help withbetter deposition of lithium upon recharging and prevention ofcatastrophic failure; it is noteworthy to mention that the aluminumlayer may be electronically insulated from at least of one electrode byan electronically insulating layer or coating (made of materials such asconventional battery separators, conventional battery binders, PE, PP,polyester, polyurethanes, PVDF, PTFE, silicone, polyimide, Al₂O₃, SiO₂,TiO₂, PEO, LIPON, etc.); this layer or coating can be selected such thatthe chance of any direct electronic contact between the oppositeelectrodes be minimized.

An example is a Li-ion battery with conventional electrodes andelectrolyte (e.g Carbon anode, LCO cathode and LFP in EC-DMC-DMEelectrolyte) where the two electrodes are separated by a layer ofperforated-porous aluminum sandwiched between two layers of PE or PPmicroporous layers (e.g., Setela or Celgard); the middle aluminum layernot only can help with the operational performance of the cell due toits excellent thermal conductivity and also electronic conductivity(easy charge separation on the surface) effect; in addition in the eventof a dendritic short (e.g., cold temperature or fast charging) themultilayer separator is now mechanically much stronger than PE-PPseparators of the same thickness and can force the dendrite to stop;Even if the dendrite penetrates the first PE-PP microporous layer, thenno catastrophic failure may happen; this is because the lithium dendriteand aluminum contact can change the redox reactions and the voltage suchthat the dendrite won't be favorable, and may disappear at the followingcycles; one possible mechanism is the that the lithium metal (from anodeor dendrite) and the aluminum may perform an in-situ compositelithium-aluminum anode, similar to that known in the art.

Another example is a Li-ion battery with conventional electrodes andelectrolyte (e.g. Carbon anode, LCO cathode and LFP in EC-DMC-DMEelectrolyte) where the two electrodes are separated by a layer ofperforated-porous aluminum that is covered by metal oxides such as Al₂O₃on the surface, where the metallic oxide may have been deposited on themetal (Al) surface or may have been formed as the oxidation of the metal(Al), for example Al₂O₃ forms on the surface by corrosion of the metal(Al); the middle aluminum layer not only can help with the operationalperformance of the cell due to its excellent thermal conductivity andalso electronic conductivity (easy charge separation on the surface)effect; in addition in the event of a dendritic short (e.g., coldtemperature or fast charging) the introduced separator is nowmechanically much stronger than conventional separators of the samethickness and can force the dendrite to stop; Even if the dendritepenetrates the first metal oxide layer, then no catastrophic failure mayhappen; this is because the lithium dendrite and aluminum contact canchange the redox reactions and the voltage such that the dendrite won'tbe favorable, and may disappear at the following cycles; one possiblemechanism is the that the lithium metal (from anode or dendrite) and thealuminum may perform an in-situ composite lithium-aluminum anode,similar to that known in the art. The thickness of the aluminum can be0.001-0.01 mm and the Al₂O₃ can be 0.0005-0.005 mm in this example. Morethan one metallic interlayer can be implemented, for example twoaluminum perforated layers that are offset (US Patent ApplicationPublication No. 2013/0224632) can be used, between the two layers can beanother oxide layer or can be a conventional polymer separator orelectrolyte such as PE-PP microporous or nonwoven films or a coating ofPEO, PVDF, LIPON, LISICON or PTFE. Note that the dendrite between anodeand the middle metal (say Al here) may melt during operation (e.g., withabout 100 mV in less than 1 ms) which increases the safety of the cell.

Another example is a lithium battery with conventional electrodes orlithium metal anode and electrolyte (e.g. carbon anode, LCO cathode andLFP in EC-DMC-DME electrolyte) where least one layer ofperforated-porous aluminum is in physical contact with an electrode,preferably the anode. Further the aluminum layer can be separatedelectronically and physically from the other electrode by means ofconventional battery separators such as micro-porous PE-PP layers. Atleast one porous metal oxides layer such as Al₂O₃ may be deposited on atleast one surfaces of the aluminum layer(s); the oxide layer can helpwith the wetting of the electrolyte surface and thus improve theperformance of the electrochemical cell, where the metallic oxide mayhave been deposited on the metal (Al) surface or may have been formed asthe oxidation of the metal (Al), for example Al₂O₃ forms on the surfaceby corrosion of the metal (Al); more than one layer of perforated-porousaluminum may be placed in the cell, for example two perforated layerswith complementary patterns of apertures may be placed according to USPatent Application Publications No. 2013/0017432 and 2013/0224632; themultilayers of perforated-porous metal (e.g. aluminum foil) may be inphysical contact or may not, if not in physical contact, then a thinmicroporous or nonwoven layers such as PE, PP separators or a layer suchas PEO or pvdf or metal oxides can be placed at least in part of thespace between the metal layers. The aluminum layer(s) not only can helpwith the operational performance of the cell due to its excellentthermal conductivity that results in more uniform heat distribution, butalso improves the mechanical stability of the cell in the event of anexternal or internal shorts such as dendritic short (e.g., coldtemperature or fast charging) where the introduced separator is nowmechanically much stronger than conventional separators of the samethickness and can force the dendrite to stop; Even if an electronicconnection between at least one electrode and the aluminum is made stillno catastrophic failure may happen; this is because the lithium dendriteand aluminum contact can change the redox reactions and the voltage suchthat the dendrite won't be favorable, and may disappear at the followingcycles; one possible mechanism is the that the lithium metal (from anodeor dendrite) and the aluminum may perform an in-situ compositelithium-aluminum anode, similar to that known in the art. The thicknessof the aluminum can be 0.005-0.01 mm and the Al₂O₃ can be 0.0005-0.005mm in this example. More than a metallic interlayer can be implemented,for example two aluminum perforated layers that are offset (see, e.g.,US Patent Application Publication no. 2013/0224632) can be used, betweenthe two layers can be another oxide layer or can be a conventionalpolymer separator or electrolyte such as PE-PP micro-porous or nonwovenfilms or a coating of PEO, PVDF, LIPON, LISICON or PTFE. Note that adendrite may melt during operation (e.g., with about 100 mV in less than1 ms).

Another benefit of the highly thermal layer in the membrane ishomogeneous distribution of heat inside the cell (reducing thermalgradient) that not only reduces the risk of catastrophic failure butalso increased the cycle life of the battery.

Example 2 Electrochemical Systems with Inserted Conductive Layers

This example relates to methods in order to stop, slow down or controlthe dendrite formation in electrochemical plating such as inrechargeable electrochemical cells with lithium metal, zinc metal oraluminum metal anodes, for example in Li-air, Zn-air and Al-airbatteries. This disclosure enables high energy, high rate and high cyclelife (high performance) rechargeable batteries. Other applications suchas electroplating gold or other materials of interest such as othermetals can also benefit from this disclosure.

Different methods are suggested for this purpose. One method is based onmanipulating the electric filed near the electrode of interest. In anyelectroplating, the electric field plays a role in the morphology andspeed of the deposition. As an example, there may be someinhomogeneities or impurities (existing such as those from the substratematerial or in situ forming such as those from the reactions between theelectrolyte and the electrode materials) on the surface which can causeuneven deposition (for example by changing the nucleation energy orelectric conductivity on the surface). This step may be governed byionic diffusion, electric insulators or nucleation or other parametersnot directly related to the electric field intensity, but after certainamount of electroplating growth or time, the electric field can startplaying a key role. Electric field near any surface is affected by thegeometry of the surface; areas with higher curvature have higherelectric field near them, e.g., surface density of charges such aselectrons and ions is much higher closer to the tips of a surface thanon the flat area of the surface. This means that after certain amount ofthe growth of the deposition, the areas with higher curvature willattract more charges, which itself results in higher curvature and thusfurther growth; this is the phenomena that results in the unevenelectroplating which gets worse with more deposition.

Different methods have been suggested in the past to overcome thismentioned uneven electroplating. One method is reducing the speed (rate)of electroplating; however in many applications such as in energystorage (e.g., batteries) there is a limit on the time that the user iswilling to wait (for example in recharging a cellphone battery, the userdoes not want to wait hours to charge his cellphone), for this reasonpulse electroplating (charging) is suggested, however, there a clearbalance between the effectiveness of pulse electroplating (charging) andthe total time of the electroplating (charging). Another suggestedmethod that has been actively explored is changing the electrolyte(environment) of electroplating. This method tries to control theinhomogeneities or impurities (nucleation sites and their growth speedat least initially) rather than the electric field related growth(previous method). However this method may result in the electrolyteconsumption in closed systems, such as in batteries, and the number ofcycles can thus be limited due to the loss of active or supporting ions;many researchers observed great results in the lab scale with smallamount of deposition quantity to electrolyte volume ratio (Ah/mL), butrealized that the method causes another fading mechanism in practicalapplications, due to the limitation on deposition quantity toelectrolyte volume ratio. Another suggested method to controlelectroplating (cycling) in electrochemical cells is applyingout-of-plane pressure on the surface of the deposited area. This methodhas been shown to be very effective to mechanically suppress the unevendeposition (the mechanical force flattens the surface). This method hasbeen proven difficult to be applied in practical situations (such as ina cylindrical battery); several novel methods have been developed topractically apply out-of-plane pressure on the surface and the resultsare very promising. In this Example the author introduces another novelmethod to control the surface of electroplating and ensuring highperformance.

Changing the Electric Field:

The new method is based on changing the electric field in the vicinityof the electrode and can be used with or without any other methods. Inthis method a layer capable of having surface charges withoutinterrupting the ionic flow between the opposite electrodes isintroduced into the space between the opposite electrodes. An examplecan be a thin (e.g., less than 0.025 mm thickness) perforated metallic(stainless steel, nickel, titanium, iron or aluminum) layer or a carbonlayer covered by thin (e.g., less than 0.025 mm) insulating layer,coating or material to ensures that there is no electronic connectioninside the cell between the opposite electrodes; thus the conductivelayer is electronically separated from the electrode of interest, e.g.,from lithium metal electrode in a rechargeable lithium battery. Examplesof the thin insulating layer or coatings are separators such as celgardor any of those described in US Patent Publication no. 2013/0224632, orsuch as polymers; e.g., PVDF, PE, PP, parylene, PTFE, PET, PEEK, LIPON,polyester, epoxy or PEO or ceramics; e.g., alumina, titania, zirconia,silica, aluminum nitride, lithium nitride, titanium nitride or siliconnitride). The conductive layer allows surface charges on its surfacesuch that the charge on surface of the conductive layer opposes thecharge on the electrode it is facing, where the electroplating ishappening. For example, the charge on the surface of the metallic layerfacing lithium in a lithium metal battery is positive during charging.Conductive layers with high charge separation (such as those used incapacitors) are preferred so that they can affect the electric fieldbetter. Higher surface area of the conductive layer (m2/gram) can thusimprove the results. The electric field changes due to the insertion ofthe conductive layer; that is the surface charges on the conductivelayer facing the electrode of interest (e.g., lithium during charging)repels the same-sign charges, which results in more homogenousdistribution of the ions in the electrolyte between the conductive layerand the electrode and thus a more uniform deposition in electroplating(or battery charging).

Changing the Thermal Field:

Another benefit of the conductive layer is that it can result in higherlife cycle and less capacity fades in the electrochemical cells. Part ofit can be because the conductive layer makes the electric field moreuniform and thus fewer hot spots may form on the electrodes. Hot spotscan form due to material impurities or due to areas with slightly highervoltage (overpotential) compared to their neighborhood and are known toresult in loss of performance in the cells. Another benefit can be dueto the fact that electronically conductive layers are also thermallyconductive; thus the conductive layer may help with more uniform thermalfield inside the cell and less temperature gradients, which results inbetter performance and higher cycle life of the cell. It can alsosignificantly improve the safety of the cell, especially in largercells, such as those used in electric driven vehicles, where a hightemperature gradient may cause not only capacity loss, but may alsoresult in fire and explosions.

Conductive Layer and the Opposite Electrode:

The conductive layer may or may not be electronically connected to theopposing electrode. Further, the conductive layer may or may not bephysically connected to the opposing electrode. Decisions should bebased on the chemistry and ionic and electronic conductivity of theopposite layer. It is expected that electronically connecting theconductive layer to the opposite electrode (not the one which we want toelectroplate on) results in higher changes in the electric field nearthe surface of the electrode of interest, due to the help from externalsource of energy during charging (electrode of interest=where we performthe electroplating such as the lithium metal electrode in a lithiummetal battery) and thus can result in more uniform electroplating on theelectrode of interest. On the other hand, electronically separating theconductive layer from the opposite layer can modify the electric fieldnear the surface of the opposite electrode which has its own advantage,including pushing the ions deeper into the opposite electrode, which canhelp with making thicker electrodes and thus higher energy cells; it mayalso improve the rate capability of the cell by allowing better ionicand electronic conductivities. It is also expected that physicalseparation between the conductive layer and the opposite electroderesults in better wetting of the opposite electrode by the electrolyteand thus better performance may be achieved; this is because theconductive layer may not be able to hold enough electrolyte on itssurface, as opposed to battery separators which are designed to holdlarge amount of electrolyte; thus surface coating (at least partially)of the conductive electrode in vicinity of the opposite electrode may beneeded to reduce the interface resistance on the surface of the opposingelectrode layers. On the other hand, it is also expected that physicalconnection between the conductive layer and the opposite electroderesults in higher electronic conductivity of the opposite electrode andthus better performance of the cell due to improving the electronicconductivity of the opposing electrode through the new path (secondarycurrent collector) provided by the conductive layer; This can also helpwith making thicker electrodes and thus higher energy cells; it may alsoimprove the rate capability of the cell by allowing better ionic andelectronic conductivities.

In an embodiment, the conductive layer does not react chemically orelectrochemically with any other component of the cell, including theelectrolyte. Thus a chemically and electrochemically resistant coatingmay be applied to the conductive layer. Examples are polymers; e.g.,PVDF, PE, PP, PTFE, PET, PEEK, polyester, epoxy, parylene, LIPON or PEOor ceramics; e.g., alumina, titania, zirconia, silica, aluminum nitride,titanium nitride, lithium nitride or silicon nitride. It is alsopreferred that the conductive layer and its potential coating layershave minimal effects to the ionic resistance of the cell, for thisreason porous or perforated conductive layers are preferred. However,the when increasing the porosity the overall performance of theconductive layer, e.g., uniform electric field and other aspects such asmechanical integrity, should be considered. Further, in some embodimentsmore than one conductive layer can be used. In some embodiments theconductive layer can be part of the separator of the electrochemicalcell.

Please refer to FIGS. 1 and 2.

Example 3 Electrochemical Cells with Improved Safety and Performance

An electrochemical cell is introduced, consisting of an anode, acathode, an electrolyte, one or more separator layer(s) and anelectronically conductive layer.

The electronically conductive layer may have no electronic connectionswith one of the electrodes or may have no electronic connections withany of the electrodes.

The electronically conductive layer can be porous, perforated, nonwovenor thin coating. The size of the holes can be from 10 nm to 1 cm,depending on the chemistry of the cell. For example in a lithium ionbattery it can be about 0.2 mm. In an alkaline battery (Zinc anode basedor Nickel cathode based) it can be about 0.5 mm. The thickness of thelayer can be less than 1 mm, preferably less than 0.1 mm depending onthe chemistry. For example in li-ion battery it can be about 0.01 mm. Inan alkaline battery (Zinc anode based or Nickel cathode based) it can beabout 0.1 mm. The layer itself can be a coating on a non-conductivelayer such as micro-porous or nonwoven PE-PP such as Celgard 2225. Thethickness of the coating can be less than 0.005 mm, for example can beabout 0.002 mm. The layer can also be made of metalized PET or metalizedpolyimides. The electronically conductive material can be made of anyelectronically conductive materials such as metals (e.g., stainlesssteel, copper, titanium, nickel, aluminum, Sn), from alloys (e.g.,alloys of the said metals), from conductive polymers, from carbon, orany combinations thereof. The porosity of the layer can be at least 30%,for example 70%.

Electrolyte can be aqueous, non-aqueous, gel, polymer (such as PEO) orceramics (such as LISICON or NASICON).

The electrochemical cells can be rechargeable or primary. They can beli-ion batteries, lithium metal batteries, Zinc anode based batteries,Nickel cathode based batteries, lead-acid based batteries or any otherbattery chemistry. They can further be any fuel cell or flow battery.

In some embodiments any or both of the separators layers can be in theform of coating layers on the said electronically conductive layer. Insome embodiments, more than one conductive layer can be used.

This disclosure relates to new applications of the electronicallyconductive layer to an electrochemical cell, such as those known in theart of energy storage.

It is known in the art that the temperature generated during an internalshort is the controlling parameter in any safety hazard. Theelectronically conductive layer prevents the expansion of any possibleinternal short in the cell, and can prevent the cell from thermalrunaway, and thus can significantly reduce the risk of fire andexplosion. In some occasions, the electronically conductive layer mayeven control the internal short, for example by burning out possibleinternal dendrites. This kind of dendrite shorts is the major culpritbehind many fire incidents in the case of too fast charging or too muchcharging (voltage) which are known to result in dendrite forming onli-ion cells. Shorts may also happen in cells with metal anodes such asin lithium metal anode cells (e.g., Li—S, Li-Air or Li—LiFePO4 cells) orzinc metal anode cells (e.g. rechargeable Zn—Ni cells).

In addition as most electronically conductive materials are alsoexcellent thermally conductive materials, the layer can result in lessheat gradients in the cell and more homogenous distribution of the heatin the cell not only in the event of a short (internal or external) butalso during the normal performance. This is especially important in highpower or fast charging rate situations. The outcome is not only saferenergy storage systems but also longer life cycle of the system.

An example is an electrochemical energy storage system for a cellphone,electronics, vehicle or utility storage that implements li-ion chemistryin cells with this arrangement:

Copper, anode Current collector/Li-metal, 0.05 mm thick/celgard, 0.012mm thick/perforated stainless steel, 0.01 mm/celgard, 0.012 mm/LiCoO₂,0.1 mm/Al, cathode current collector.

In some embodiments the electronically conductive layer can have asurface charge. In some embodiments the surface charge can increase thecycle life of the energy storage system. As an example a positivesurface charge may reduce the dendrite formation or growth; for examplein a cell with metallic anode, such as lithium or zinc. As anotherexample the surface charge may hinder the migration of polysulfide froma sulfur cathode to anode in a li-ion cell.

It is noted that the conductive layer should not react chemically orelectrochemically with any other component of the cell, including theelectrolyte, during the normal life of the electrochemical cell. In someembodiments, a chemically and electrochemically resistant coating may beapplied to the conductive layer.

Example 4 Active Membranes: Conductivity Assisting Membranes and theirUse as Active Separators in Electrochemical Cells Such as BatteriesSummary

In this disclosure, active membranes are introduced, especially asseparators in electrochemical cells such as in batteries. In anembodiment, the disclosure provides a multi-layer membrane comprisingtwo or more layers such that at least one of the layers at either of theends of the membrane is electronically conductive; and at least one ofthe middle layers is electronically nonconductive such that there is noelectronic connection between the two outer faces of the membrane. Inembodiments, some of the layers are deposited or coated on each other.In an embodiment, some of the layers are deposited or coated on anotherlayer or on either of the electrodes.

The multi-layer membranes of the present disclosure are capable of beingused as a separator in an electrochemical cell. In an embodiment, theouter conductive layer results in a new electronic path for the outerparticles of the adjacent electrode and thus increases the electronicconductivity of the adjacent electrode materials. In an embodiment, theouter conductive layer results in a change in electric field at least inthe vicinity of the corresponding electrode

In an embodiment, each of the conductive layers is a porous orperforated layer or a mesh made of a metal such as stainless steel oraluminum or copper. In an embodiment, the porosity of the metallic layeris at least 30%. In an embodiment, a metallic conductive layer isbetween an electrode and an electronically non-conductive layer of themembrane. In an embodiment, a non-conductive layer is a coating on oneside of the metallic layer; in an embodiment the coating is a polymersuch as PTFE or PVDF or PEO or PMMA.

In embodiments, the total thickness of the membrane is less than 500micrometers or less than 25 micrometers. In an embodiment the ionicresistance of the separator is less than 10 ohm·cm².

In an embodiment, an electrode material undergoes shape change due tocharging-discharging, which can result in the loss of at least part ofthe electronic conductivity between the electrode materials and thecorresponding current collector.

In an embodiment, the membranes of the present disclosure are used as aseparator in an electrochemical cell such as a rechargeable lithiumbattery. In an embodiment, a lithium battery is made with separator ofthe present disclosure. In an embodiment, the anode is silicon. In anembodiment, the cathode is lithium oxide or is sulfur or is carbon orair. In an embodiment, the electric field modifications due to theconductive layer of the separator result in a more uniform lithiumdeposition during charging and thus increases the performance, lifecycle and efficiency of the electrochemical cell. In a furtherembodiment, an alkaline battery made with a separator of the presentdisclosure. In another embodiment, a metal air battery made with theseparator of this disclosure.

In an aspect, the methods of the disclosure are used inelectro-depositions such as in electro-depositing of a metal such asgold, silver or lithium or zinc or copper or an alloy.

An Example of the usage of the membrane as a separator in anelectrochemical cell such as in a battery: FIGS. 14-17: black: currentcollectors (at extreme right and left), medium gray circles: activeelectrode particles (e.g. Silicon), medium gray line segments: carbonblack, double gray lines: conventional separator, double black lines:our separator, darker gray circles are the in-active (lost) electrodematerial due to the lost electronic connectivity. Dark gray: oppositeelectrode. Electrolyte is white.

FIG. 14 shows the battery before use. All of the electrode particles areelectronically connected.

FIG. 15 shows the battery after charging, the electrode particles have alarge shape change.

FIG. 16 shows the battery, with the conventional separator, afterseveral cycling, some of the electrode particles have lost theirelectronic connection with the current collector and thus are in-active.

FIG. 17 shows the battery, with the new separator, after severalcycling, some of the electrode particles have lost their conventionalelectronic connection with the current collector but the new separatorprovides a new path for some of the electrode particles. The new path ofthe electrons, due to the new separator is shown in gray.

Example 5 Multi-Layer Separators

Abbreviations for layers:

-   -   eNc: electronically Nonconductive    -   eC(R): electronically Conductive, Reactive with dendrite    -   eC(nR): electronically Conductive, non-Reactive with dendrite    -   eC(R/nR): part nonreactive, part reactive with the electrolyte        (for example a coating of reactive on a nonreactive).    -   eCS: a matrix of electronically conductive with solid material        fibers or particles (the solid electrolyte particles fill the        pores-holes of the matrix). The solid electrolyte fiber        particles can be a known solid electrolyte such as known polymer        or ceramic solid electrolytes. In an embodiment, this layer        comprises a porous layer of electronically conductive material        and at least a group of fibers or particles filling the        pores/holes of the porous layer.    -   NOTE: Each of the above can be: a free standing microporous or        non-woven layer; or can be a coating on any of the electrodes or        on another layer of the separator)

Combinations of the Multi-layer separators between anode and cathodeelectrodes:

-   -   At least one eNc layer and at least one eC(R) layer    -   At least one eNc layer and at least one eC(nR) layer    -   At least one eNc layer and at least one eC(R/nR) layer    -   Any combination of at least one eNc and at least one eC layer,        such that there is no electronical conductivity between the        opposite electrodes    -   The eC layers can have an external tab    -   The external tab can be used passively to monitor the voltage        between the eC layer and any of the electrodes (USC paper) or        can be used actively (applying voltage or current between the eC        layer and any of the electrodes.

With solid electrolyte

-   -   The eC layer can be eCS    -   The solid electrolyte can be a free standing layer or a coating        layer; or can be a component of the eC or eNc layers, e.g.,        particles or fibers filling the holes-pores of the eC or eNc        layers    -   The solid electrolyte material can be any of the traditional        solid electrolytes (transporting ions without any applied        voltage or current at the eC layer, such as LISICON or PEO), or        can be made of a nontraditional solid electrolyte, such as        traditional electrode active material (transporting ions without        any applied voltage or current at the eC layer, such as LiTiO2,        Silicon or Graphite); the applied voltage can be direct current        or non-direct such as a sinusoidal voltage varying between the        charge-discharge voltages of the nontraditional solid        electrolyte.

In-situ lithiation in Li-ion batteries

-   -   Any of the eC or eNc layers may have a lithium metal coating.    -   Any of the eNc layers can be made of lithium (porous or not        porous).    -   The excess lithium can be used to lithiate the electrodes (if        not lithiated electrodes are used such as silicon anode and        sulfur or air cathode) or can compensate for the ions loss (SEI,        . . . ).    -   Applied voltage or current to the lithium layer may be necessary        via external tab, for example pulse or sinusoidal between 1 and        2.5V applied between a graphite anode and the eCS (LiTiO2 fibers        inside a copper matrix) in a li-ion cell, for example with an        air or sulfur electrode.

Example of Combinations of the Multi-layer separators between anode andcathode electrodes:

-   -   eNc-eC-eNc    -   eNc-eC-eNc-eC    -   eC-eNc-eC-eNc-eC    -   eNc-eCS-eNc-eC    -   eC-eNc-eCS-eNc-eC    -   eC-eNc    -   eC-eNc-eC    -   eC-eNc-eCS    -   eCS-eNc    -   eCS-eNc-eCS    -   eCS-eNc-eC

Any electrochemical cell

-   -   Li-ion batteries    -   Li-metal batteries    -   Metal-air batteries    -   Alkaline batteries    -   Zinc batteries    -   Metal hydride batteries    -   Lead-acid batteries    -   Rechargeable or primary batteries    -   Flow batteries, fuel cells, semi-solid batteries

Example 6 Exemplary Electrochemical Cells

Cell 1: A rechargeable lithium metal pouch cell containing EC: EMC (3:7w %)-1.2M LiPF6 electrolyte, Toda NMC (111) Cathode active wt: 0.2021 g,and lithium metal anode. The area of the cathode is about 20 cm². Theseparator is a multilayer film with a perforated 0.015 mm thick aluminumlayer placed between two microporous polyethylene layers, each 0.007 mmthick, without adhering the layers. The aluminum layer has a periodicpattern of holes with 0.300 mm diameter and 0.300 pitch. Specificcapacity at 12 mA discharge is 29.91 mAh. FIG. 11 shows the performanceof the cell.

Cell 2: A rechargeable lithium-Sulfur pouch cell containing EC: EMC (3:7w %)-1.2M LiPF6 electrolyte, Sulfur-Carbon cathode active wt: 0.2021 g,and lithium metal anode. The area of the cathode is about 20 cm². Theseparator is a multilayer film with a perforated 0.007 mm thick copperlayer placed between two nonwoven polyester layers, each 0.01 mm thick,without adhering the layers. The conductive layer has a periodic patternof holes with 0.300 mm diameter and 40% porosity.

Cell 3: A rechargeable lithium ion pouch cell containing EC: EMC (3:7 w%)-1.2M LiPF6 electrolyte, LiFePO₄ Cathode active wt: 0.2021 g, andsilicon-graphite anode. The area of the cathode is about 20 cm². Theseparator is a multilayer film with a porous 0.01 mm thick conductivecarbon/super-P layer placed between two microporous polypropylenelayers, each 0.007 mm thick, with pvdf/PEO-NMP/acetone-evaporationadhering the layers. The conductive layer has 40% porosity. The glue is50% pvdf powder, 50% PEO powder dissolved in 50% NMP, 50% acetone, whichis sprayed on the corresponding sides of the separator.

Cell 4: A rechargeable Zn—Ni pouch cell containing 6 M KOH electrolyte,NiOOH cathode, and Zn—ZnO anode. The area of the cathode is about 20cm². The separator is a multilayer film with a perforated 0.007 mm thickstainless steel layer placed between two microporous polyethylenelayers, each 0.007 mm thick, without adhering the layers. The conductivelayer has a periodic pattern of holes with 0.300 mm radius and 0.300pitch.

Cell 5: A rechargeable lithium air cell containing EC: EMC (3:7 w%)-1.2M LiPF6 electrolyte, carbon air cathode, and lithium metal anode.The area of the cathode is about 20 cm². The separator is a multilayerfilm with a perforated 0.003 mm thick stainless steel layer placedbetween two microporous polyethylene layers, each 0.007 mm thick, whichwere adhered by heating and pressure. The conductive layer has anarbitrary pattern of holes with 0.100 mm radius and 0.200 pitch.

Cell 6: A rechargeable lithium ion pouch cell containing EC: EMC (3:7 w%)-1.2M LiPF6 electrolyte, LiCoO₂ Cathode active wt: 0.2021 g, andgraphite anode. The area of the cathode is about 20 cm². The separatoris a multilayer film with a 0.001 mm conductive PDOT-PSS-PANi basedpolymer deposited on one side of two microporous polyethylene layers,each 0.007 mm thick, with heat-press adhering the layers. The conductivelayer has 70% porosity.

Cells 7-12: Cells 1-6 where one of the microporous PE layer of themultilayer separator is removed.

Cells 13-18: Cells 1-6 where the multilayer separator has anotherconductive layer next to the anode.

Cells 19-24: Cells 1-6 where the multilayer separator has anotherconductive layer next to the cathode.

Cells 25-30: Cells 1-6 where the multilayer separator has two otherconductive layers, each next to an electrode.

Cells T1-T30: Cells 1-30 where each conductive middle layer has anexternal tab to monitor the voltage between the conductive layer and theelectrodes. After observing a voltage variation between the conductivelayer and any of the electrodes, indicating an abnormality on the cell,a current is applied between the conductive layer and the said electrodesuch that the said voltage variation disappears.

Cells AT1-AT12: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode is the same as the cellvoltage at any given time.

Cells AT13-AT24: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the cathode is the same as thecell voltage at any given time.

Cells ATH1-ATH12: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode is half of the cellvoltage at any given time.

Cells ATH13-ATH24: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode varies between zero andcell voltage at a frequency of 1 kHz.

Cells ATH25-ATH36: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode varies between zero andcell voltage at a frequency of 100 Hz.

Cells ATH37-ATH48: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode varies between zero andcell voltage at a frequency of 10 kHz.

Cells ATH49-ATH60: Cells 1-12 where external tabs are used to apply avoltage between each conductive layer and each electrode. The appliedvoltage between a conductive layer and the anode varies between zero andcell voltage in pulses with 1 minute duration at zero, one minute atrest (no applied voltage) and one minute at cell voltage.

Cells B1-B6: Cells 25-30 where each conductive layer has an external taband the applied voltage between each conductive layer and the electrodecloser to it is zero.

Cells B7-B12: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between each conductive layer and theelectrode further away from it to it is zero.

Cells B13-B18: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between the two conductive layers is zero.

Cells B19-B24: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between the two conductive layers is halfthe cell voltage, such that the direction of the generated electricfield is the same as the cell internal electric field.

Cells B25-B30: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between the two conductive layers is halfthe cell voltage, such that the direction of the generated electricfield is opposite the cell internal electric field.

Cells B31-B36: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between the two conductive layers variesbetween zero and the cell voltage with 10 kHz frequency.

Cells B37-B42: Cells 25-30 where each conductive layer has an externaltab and the applied voltage between the two conductive layers variesbetween zero and the cell voltage with a pulse pattern of 1 minute witha 2 minute rest in between.

Cells S1-S12: Cells 1-12 where the porosity of the conductive layer isfully filled with a polymer solid electrolyte, here PEO-LIPON based,such that the electrolytes on the opposite sides of theconductive/PEO-LIPON layer would not mix. In cell S5, the electrolyte onthe air cathode side is replaces with an aqueous electrolyte, based on3M LiOH salt.

Cells S13-S24: Cells 1-12 where the porosity of the conductive layer isfilled with a ceramic/glass solid electrolyte, here LISICON based, suchthat the electrolytes on the opposite sides of the conductive/LISICONlayer would not mix.

Cells S25-S36: Cells 1-12 where the porosity of the conductive layer isfilled with 100 nm Li₃N, such that the electrolytes on the oppositesides of the conductive/Li₃N layer would not mix.

Cells S27-S48: Cells 1-12 where the porosity of the conductive layer isfilled with a catalyst, here MnO₂ and platinum based, that assists thecycling of the cell.

Cells S49-S60: Cells 1-12 where the porosity of the conductive layer isfilled with an ion-selective filler, here Nafion based including sodiump-styrenesulfonate, lithium stearate and polydipamine, that only allowsthe transportation of negative ions through.

Cells S61-S72: Cells 1-12 where the porosity of the conductive layer isfilled with TiO₂/LTO filler such that the electrolytes on the oppositesides of the conductive/TiO₂/LTO layer would not mix.

Cells RS1-RS12: Cells 1-12 where the porosity of the conductive layer isfilled with a redox shuffle filler, here perfluoro aryl boronicesters/fluorinated1,3,2-benzodioxaborole/2,5-di-tert-butyl-1,3-dimethoxy-benzane/TEMPO,such that the cell is protected by the redox shuttle agent in the eventof an overvoltage.

FIG. 8 provides a plot of capacity (mAh) versus cycles for a LiTiO2,Toray, Al, lithium cell of the present invention having a compositeseparator with an electronically conductive layer. FIG. 9 provides aplot of capacity (mAh) versus cycles for a LiTiO₂, Celgard, Cu, lithiumcell of the present invention having a composite separator with anelectronically conductive layer. FIG. 10 provides a plot of capacity(mAh) versus cycles for a LiTiO₂, Celgard, Ni, lithium cell of thepresent invention having a composite separator with an electronicallyconductive layer. The plots shown in FIGS. 8-10 show a variety of sharppeaks (e.g., at about 200 cycles in FIG. 8, about 65 cycles in FIG. 9,about 80 cycles in FIG. 10) that are believed to correspond to theformation of a short in the electrochemical cell. As shown in the plots,however, theses peaks are followed by a return to normal capacities forsubsequent cycles. In some embodiments, it is believe that the formationof the short results in an alloy reaction, for example, involving thelithium dendrite and the aluminum electronically conductive layer of thecomposite electrode that results in the consumption and/or dissipationof energy. In some embodiments, the peak is most pronounced duringcharging, which is believed to correspond to an electrical short beingburned out during the charge cycle.

FIG. 11 provides a plot of capacity (mAh) versus cycles for a pouch cellcontaining EC: EMC (3:7 wt %)-1.2M LiPF₆, Toda NMC(111) vs. Li. Cathodeactive wt: 0.2021 g and having a composite separator with anelectronically conductive layer. The results shown in FIG. 11 show aspecific capacity at 12 mA discharge equal to 148 mAh/g. The cyclingbehavior shown in FIG. 11 is consistent with an avoidance of a short,for example, due to the electrical field provided by the electronicallyconductive layer of the composite separator of this embodiment.

Example 7 Electrodes, Separators, Membranes, Current Collectors andElectrochemical Cells

The electrochemical cells in this disclosure include, but are notlimited to, batteries, fuel cells, flow batteries and semi-solidbatteries. Any of the electrode active materials can be solid, liquid,gas, flowable semi-solid or condensed liquid composition. A flowableanodic semi-solid (also referred to herein as “anolyte”) and/or aflowable cathodic semi-solid (also referred to herein as “catholyte”)are/is comprised of a suspension of electrochemically-active agents(anode particulates and/or cathode particulates) and, optionally,electronically conductive particles (e.g., carbon). The cathodicparticles and conductive particles are co-suspended in an electrolyte toproduce a catholyte semi-solid. The anodic particles and conductiveparticles are co-suspended in an electrolyte to produce an anolytesemi-solid. All voltages are wrt Li₊/Li.

Composite Separators and Functionally Graded Separators

Several novel separators and membranes for electrochemical cells andelectrochemical cells employing such separators-membranes areintroduced. In an embodiment, use of these separators results inbatteries (primary or rechargeable) with better performance than stateof the art as an example rechargeable lithium metal based batteries,rechargeable zinc metal based batteries and longer life cycle siliconbased lithium ion batteries are possible, also are fast charge, highpower li-ion batteries and long life alkaline and lead-acid batteries.For example, the performance of the battery may be improved over thoseincluding separators and membranes made in a symmetric form such thatthe porosity and structure of the separator is the same at any depththrough the thickness of the separator.

Composite separators include separators that have different amounts orforms of openings through the thickness, for example the two sides aredifferent from each other or/and the sides are different from theinterior. The different amount of porosity and the structure of theporosity (e.g., size of the holes) are designed such that they match therequirements of the adjacent electrode. This is expected to result inbetter performance of the electrodes and electrochemical cells as theseparator-electrode interface plays a role in the performance (such asrate needed for fast charging and high power and cycle life) of theelectrochemical cell. Some electrodes (e.g., lithium battery cathodematerials, such as lithium metal oxides) need more electrolyte in theirvicinity to keep the surface homogeneously wet (this can be due todependence of the ionic conductivity of the electrode on the chargestate, e.g. Li1-xFePO4 or Li1-xCoO2 have different ionic conductivitiesdepending on the values of x) thus require a very porous interface withthe electrolyte (at least 40% porosity on the separator interface). Anexample can be a nonwoven separator or a ceramic coated separator. Onthe other hand some electrodes (such as metals e.g. lithium, silicon,zinc, Mg, lead, aluminum) perform better (e.g. better recharging andcycle life) when there is a confining force on their surface (the out ofplane pressure on the surface or tension in the plane from the sides canresult in a smoother deposition during electroplating the ions); thushere a stronger and less porous separator interface is preferred, anexample can be a micro-porous separator, elastomer-material separator orthe separator as described in US Patent Application Publication2013/0224632. As the result a non-symmetric separator with differentproperties on each of the sides is of great interest. The separator canbe a multilayer separator in which each layer has a different property,as an example an electrochemical cell with lithium metal anode andlithium metal oxide cathode can be made in which the separator is a twolayer separator consisting of a nonwoven layer (e.g. 0.01 mm thick) onthe cathode side and a mechanically strong layer (e.g. 0.01 mm thickmicro-porous or a polymer electrolyte or a solid electrolyte.) on theanode side. The layers can be laminated to each other by the methodsknown in the art such as using binders and/or applying heat-pressure.Any electrolyte such as non-aqueous, organic electrolyte, aqueouselectrolyte, polymer electrolyte or solid (such as ceramic) electrolytecan also be used.

As another example, an electrochemical cell may have electrodes thatprefer less resistance, for example more porosity in the electrode andin the separator, at the interface with the separator. However, to keepthe mechanical integrity of the separator and/or preventing any shortsbetween the opposite electrodes, a stronger and/or less porous layer isneeded to be placed in the interior; thus a multilayer separator can beformed. The exterior layers can be highly porous nonwoven layers and theinterior can be a micro-porous layer or a polymer electrolyte or a solidelectrolyte. The layers can be laminated to each other by the methodsknown in the art, such as using binders and/or applying heat-pressure.Any electrolyte can be used. For a multilayer separator such as thoseintroduced here or the conventional multi-layer separators known in theart, the change in the layers' properties of the separator can bedesigned such that the interface resistance is minimized, this can bedone for example by designing functionally graded multi-layer separatorwhere the porosity and structure of the pores vary gradually to minimizethe ionic resistance of the separator which itself increases the rateand cycle life performance of the electrochemical cell.

Composite separators also include those described in US PatentApplication Publications 2013/0017432 (Roumi) and US 2013/0224632(Roumi).

Buffer Separators:

An electrochemical cell may perform better if out of plane pressure isapplied on the surface of at least one of the electrodes (such aslithium, silicon, zinc, Mg, lead, Aluminum). One example is metalliclithium anode which gets thinner during dissolution (discharge); howeveron the recharging lithium metal is known to deposit non-smoothly whichresults in electrolyte loss (due to repetitive SEIformation-destruction) and possible dendritic growth of the metal.Mechanical pressure is shown to mitigate or even prevent thisnon-uniformity. However, current state of the art such as micro-porousseparators may not be able to apply the desired pressure after theelectrode thickness (and thus the cell thickness) is decreasedsignificantly due to discharging, due cycling for example because of thecreated gaps between the electrode and the separator at least onelocation; examples are cells made with lithium, zinc-oxide or lithiatedsilicon electrodes when they get smaller due to losing material. Thus, aseparator that can act as an elastomer is of interest. Another exampleis a silicon electrode which undergoes large deformation inelectrochemical cycling which results in electrolyte loss (due torepetitive SEI formation-destruction) and active material capacity loss(electronic isolation). Here a separator is introduced which can alsoact as an elastomer or buffer such that the surface of the electrode isunder pressure. An example of such a separator is a multilayer made witha mechanically strong layer on the electrode side (such as the lithiumanode or silicon anode) and a deformable, elastic, or spongy layermaking the rest of the separator or making the interior of theseparator. The deformable, elastic or spongy layer can be for example aporous or perforated layer or foam sheet. It can be made of for examplesilicone, rubber, PP, PE, polyurethanes, polyesters or other materialsknown in the arts of membranes and elastomers. It can also be made ofmetallic materials or alloys such as metal foams (e.g., Ni-foam ortitanium foam) that may also be coated by electronically insulatinglayers.

Elastomeric Current Collectors:

Several novel current collectors for electrochemical cells andelectrochemical cells employing such current collectors are introduced.It is expected that this results in batteries (primary or rechargeable)with better performance than state of the art, as an examplerechargeable lithium metal based batteries, rechargeable zinc metalbased batteries and longer life cycle silicon based lithium ionbatteries are possible, also are fast charge, high power li-ionbatteries and long life alkaline and lead-acid batteries. State of theart current collectors for batteries including alkaline batteries andli-ion batteries are made of very thin (0.01 mm thick) sheets of metalssuch as copper and aluminum. The main functionality of the currentcollector is transporting electrons between the inside and outside ofthe cell. However, current collectors occupy volume and add to theweight of the cell so it is beneficial to use them for other advantages.As an example, an electrochemical cell may perform better if out ofplane pressure is applied on the surface of at least one of theelectrodes (such as lithium, silicon, zinc, Mg, lead, Aluminum). Oneexample is metallic lithium anode which gets thinner during dissolution(discharge); however on the recharging lithium metal is known to depositback non-smoothly which results in electrolyte loss (due to repetitiveSEI formation-destruction) and possible dendritic growth of the metal.Mechanical pressure is shown to mitigate or even prevent thisnon-uniformity. However, current separators, due to the created gapsbetween the cell components, may not be able to apply the desiredpressure after the electrode thickness (and thus the cell thickness) isdecreased significantly during different steps of cycling. Thus, acurrent collector that can act as an elastomer is of interest. Anotherexample is a silicon anode in a li-ion battery which undergoes largedeformation in electrochemical cycling which results in electrolyte loss(due to repetitive SEI formation-destruction) and active materialcapacity loss (electronic isolation).

New current collectors are introduced which can act as elastomers orbuffers and keep the surface of the electrode under pressure duringcycling to improve the performance and cycle life. An example of such acurrent collector is a multilayer made with a high electronicallyconductive layer on the electrode side (such as the lithium anode orsilicon anode) [or the exterior sides of the current collector] and adeformable, elastic, or spongy layer making the interior [or back] ofthe current collector. The deformable, elastic or spongy layer can befor example a porous, perforated layer or foam sheet. It can be made offor example silicone, rubber, PP, PE, polyesters, polyurethanes or othermaterials known in the arts of membranes and elastomers. It can also bemade of metallic materials or alloys such as metal foams (e.g., Ni-foamor titanium foam) that may be coated by corrosion protective layers. Thethickness of the new current collector in the compressed state (forexample in the full charge state in lithium batteries) is preferred tobe comparable to the state of the art current collectors (e.g., 0.01 mmin lithium batteries). The thickness in the decompressed state (e.g.,after discharge in lithium batteries) can be bigger (for example 10% to1000% strain in the out of plane direction) such that necessary out ofplane pressure can be applied on the electrode materials (for example afew KPa to hundreds of MPa). [“Plane” is defined as parallel to theelectrode surface.]

Another example of elastomeric current collector is a composite currentcollector made of a chemically inert polymer as the middle layer andmetallic layers on the sides; the polymer layer can further increase thetensile strength of the current collector which is necessary fir windingand fabrication. One major benefit of such a current collector is lowerweight and ease of fabrication in contrast to conventional currentcollectors (e.g., 0.005 mm thick PP or silicone film with a double sidecoating of 0.001 mm copper can serve as an anode current collector forlithium batteries, especially rechargeable li-ion with silicon anode);Further the polymer can have elastomeric behavior either due to thematerial (e.g., rubber, silicone, etc.) or due to the design, such as apolymer layer that has a homogeneous distribution of trapped voidsinside (e.g., in the above example, the PP or silicone layer can have adistribution of microvoids, the microvoids can be filled with an inertgas such as argon. The microvoids in this example are compressible andthus provide the necessary elastic deformation during charge-dischargeor due to external forces).

The current collector can further be pre-stressed to improve thecharge-discharge performance of the electrochemical cell for examplecurrent collectors which have undergone pretension in out-plane orcompression in-plane will apply out-plane compressive or in-planetensile force on the electrodes which improves the performance of theelectrode.

Electrodes with Elastomeric Frames or with Mechanically Strong Frame:

A novel electrode structure and electrochemical cells (e.g.,rechargeable lithium batteries, alkaline batteries) implementing suchelectrode structures are introduced. The electrode structure implementsa frame structure that helps mechanically holding the electrode activematerials (e.g. Lithium, silicon, Sn, zinc or zinc oxide). The currentcollector is at least partially disposed within the suspension such thatthe suspension substantially encapsulates the said current collector.The structure can be in the form of a mesh, such as a metallic mesh madeof materials and/or coatings that do not fail (i.e., dissolution,corrode) during the operation of the electrochemical cell (e.g., made ofTi, TiO₂, Al₂O₃, PE, PP, Ni, Sn, Fe, Stainless steel, etc.). The framestructure not only reduces the weight and cost of the inactive materials(such as electrode binders) but also increases the cycle life andperformance. The frame can be pre-stressed before cell assembly to applyin-plane or out-of-plane forces on the active material; for example aframe that has been pre-stressed under compressive in-plane forcesduring the poring/coating of active materials will apply in-planetensions to the electrode and thus mechanically (e.g., with theassistance of positive Poisson's ratio) holds the active materials inplace even during the operation of the electrochemical cell (manyelectrodes undergo deformations due to discharging/recharging the cell);further this helps with reducing the damage to the electrodes due tooperations (e.g., silicon anode undergoes very large deformations thatshorten the cycle life of the li-ion battery). In some embodiments, thementioned frame can be made of mechanically strong materials (such asmetals or alloys, e.g., stainless steel, copper, aluminum, titanium ornickels, or such as ceramics, e.g., Al₂O₃, TiO₂, SiO₂, Al₂O₃, glass, orsuch as plastics, e.g., PVC, polyurethanes, PP, PE, or any combinationsof them) that can be further useful in protection of the cell in theevent of an applied external force that would otherwise cause the activematerials penetrate the separator and short the cell. In someembodiments, at least one part of the mentioned frame is made ofmaterials that are very deformable such as elastomers (e.g., rubber,silicone) that can act as a buffer for deformations due to the cyclingof active electrode materials; this is especially useful to prolong thecycle life of the electrodes, e.g., silicon and tin undergo very largedeformations upon lithiation that can significantly shorten the cyclelife; the elastomer frame can mitigate this problem. In some embodimentsthe frame is made of electronically conductive materials (e.g. PAN, Cu,Al, Ti) that can help with decreasing the electronic resistivity of theelectrode which can also help with enabling thicker electrodes and thushigher energy density electrochemical cells. In order to have thickerelectrodes ionic conductivity and electronic conductivity of theelectrode should be maintained through the thickness. One way of doingthis is by making connected pores in the electrode, while preventingclogging by binder and conductive carbon particles which reduces theionic conductivity through the thickness (e.g., the work by Yet MingChiang). The frame structure can also increase the thermal and/orelectric field homogeneity of the electrode and thus improves theperformance of the electrochemical cell. It is noted that although somebasic structure is used for lead acid batteries, the current inventionis far beyond that and also is applicable to not only lead acidbatteries but also lithium batteries and other alkaline batteries; e.g.,the lead acid frame is rigid and not pre-stressed, but our frame can bevery deformable acting as an elastomer or buffer for operational orexternal caused deformations of the electrode. Another example is alithium battery with lithium metal anode pressed into a metallic gridsuch as stainless steel, Titanium, nickel or copper grid such that inthe winding of the wound cells such as 18650 cells, there is no need forsputtering lithium on the current collector to enable strength fortensions during winding; as the grid itself may be exposed at the twoends, during the winding, which can carry the tension load of windingwithout breaking apart the lithium; this greatly reduces the cost of thelithium metal anode fabrication.

Electrodes with Patterns:

It is known that mechanical energy (stress and strain) plays a role inthe performance (e.g. cycling rate and lifetime) of electrochemicalcells (Farshid Roumi, PhD thesis 2010 Caltech). It is also known thatthe mechanical energy (including elastic energy) can be reduced bydesigning the optimized geometry for example by specific patterns of theelectrode. An example is a periodic pattern (straight, staggered, etc.)in which the electrode has two different thicknesses, e.g., a metallithium anode (or Zn, ZnO, Lead, lead oxide or Si) with a periodic arrayof circles (e.g., 0.5 mm diameter) with the thickness of 0.025 mm insidethe circles and 0.02 mm anywhere else. Further, in some embodiments, thecell can have a multilayer separator such that it matches the electrodein a way that there is always good physical contact between theelectrode and the separator; for example for our periodic electrodelayer, the separator can consists of several layers such that the layernext to the electrode can be 0.005 mm with a periodic hole structurethat matches the electrode structure such that the total thickness ofthe electrode and this separator layer is uniformly 0.025 mm. Theseparator can further have another layer complementary to the first saidlayer (see US Patent Publication no. 2013/0224632) such that theelectrode surface is completely in contact with the two separator layers(the 0.02 mm parts in contact with the first said separator layer andthe 0.025 mm parts with the second said separator layer); The separatorcan further have other layers, for example a nonwoven layer next to LCOcathode is preferred. In some embodiments, the current collector canalso have a pattern such that the pattern matches the electrode layersuch that the total thickness of current collector and electrode staysuniformly the same, e.g., for the above electrode pattern, the currentcollector can be 0.005 mm with a periodic hole or trench structure thatmatches the electrode structure such that the total thickness of theelectrode and current collector is uniformly the same everywhere. Eitherof the patterned current collector or separator layer can further havesome elastomeric parts, e.g., the current collector can be a compositematerial made of both electronically conducive metallic materials andelastomer materials.

Electrodes with Elastomer Particles:

Such as argon bubbles, polymers or voids trapped in the electrode. Thevolume of the argon bubbles, polymers or voids around 5% of the totalvolume. The argon bubbles, polymers or voids acting as cushions toaccommodate the shape changes during the cycling.

Safer Batteries:

Overvoltage protection and Safe-short separators and electrochemicalcells implement them: Instability of cathode and anode due to overchargecan result in a thermal event. Currently, Overcharge protection isprovided by the battery management system (BMS) Electronics add weight,volume, and cost to the pack. Redox shuttle compounds could eventuallyreplace or reduce the role of the BMS Redox shuttle (RS) compounds havea reduction-oxidation reaction at the potential where overvoltageprotection is desired•When this overpotential voltage is reached duringcell charging, the extra charge is used to oxidize the RS additive atthe positive electrode instead of further charging the cell; the cellvoltage is pegged•The oxidized form of the redox shuttle additivemigrates to the anode, where it is reduced. This process could occurindefinitely for a species that exhibits completely reversibleelectrochemical behavior and has chemically stable oxidized and reducedforms; however current electrochemical cells which use redox shuttlecompounds as additives to electrolyte suffer from negative effects onthe normal operational performance; in addition the shuttle process isnot fully reversible; thus there is a major challenge in the optimumamount of the RS additive that doesn't affect the normal performancenegatively but can perform well in the event of an overvoltage. In anembodiment, using the RS is used not as an additive to the electrolytebut as one of the components of the separator material; e.g. a thinlayer of coating on at least one perforated layer of a multilayerseparator, in which the separator has at least one perforated layer withminimum of 30% porosity or as a thin layer of coating on a nonwovenseparator or micro-porous separator, the adhesion can be made by methodsknown in the art such as, but not limited to, dip-coating, heat sealingand adhering (e.g. with pvdf, ptfe or PEO). One advantage is that due tothe possibility of using much larger amount of RS compared to theconventional electrolyte-additive method (which are current-densitylimited), the performance of the RS in the event of overvoltage issignificantly improved; especially the RS performance can last for manycycles, in contrast to current state of the art RS additives thatprovide protection only for a few cycles. An example of RS materials isPerfluoro Aryl Boronic Esters, A fluorinated 1,3,2-benzodioxaborole(BDB)•Redox voltage is about 4.43 V•Good redox shuttle candidate for NMCcathodes which operate at 4.1 to 4.2 V. Another RS material is2,5-Di-tert-butyl-1,3-dimethoxy-benzene (DDB) is a well-known,well-characterized redox shuttle compound•Its E0 of about 3.9 V is toolow for NMC cathodes but well-suited for LFP cathodes. Some otherexamples are TEMPO, MPT,1,4-di-tert-butyl-2,5-bis(2,2,2-trifluoroethoxy)benzene, lithium boratecluster salt, Li2B12H12-xFx (x=9 and 12) and other known RS materials inthe art. It should be emphasized that our approach is chemistry-agnostic(chemistry-indifferent) and can be used with any of the knownelectrochemical systems (electrolyte, electrodes and RS materials) oncethe suitable voltages are identified.

This layer or coating can be selected such that it reacts with thematerials inside the cell such as the electrolyte, upon activation (forexample due to overvoltage or excess heat or pressure). This reactionconsumes energy and reduces the failure severity and chance for exampleby the disappearance of the insulating layer or by uncovering theunderneath metallic layer that can further change the nature of thefailure. Other additives to the electrolyte can also be introduced inthe form of coating or layers of the separator.

Ionic Diodes as Separators or Electrolytes

in electrochemical cells such as batteries (e.g., li batteries, alkalinebatteries, air batteries etc.), fuel cells, flow batteries or semisolidbatteries are introduced here. Ionic diodes are well known in biology,especially cell membranes, however has never been used inelectrochemical cells. In the present disclosure ionic diodes, in theform of a pair of one directional ion channels with opposite directions,are used as components of the separator and/or electrolyte. Each ionicdiode has a minimum required concentration or voltage that ions lessthan that certain minimum concentration or voltage can't enter thechannel. Only one set of the channels is active at any time. One set isactive during the charge transporting the ions from the cathode to theanode, and the other set of channels is active during the discharge. Theionic diode can be designed based on concentration or voltage gradientsbetween the opposite ends. Also see FIG. 11.

An electrochemical cell (preferably rechargeable) is introduced in whichmore than two active materials (conventional electrochemical cell haveone anode active material and one cathode active material) are used in alayered format such that at least one active material layer is placedbetween the anode primary active material and cathode primary activematerial; primary active material is defined as the active material thatis in direct physical and electronic contact with a current collector.As an example, consider a rechargeable lithium battery consisting of (inorder of placement) anode current collector (such as a foil or mesh madeof copper, stainless steel, iron, Ti, Ni, or any other highlyelectronically conductive material), first active anode (such as lithiummetal anode or a silicon anode that may have conductive carbon added),separator and electrolyte (such as aqueous electrolyte or non-aqueouselectrolyte and micro-porous or nonwoven PE-PP separator, or solidpolymer electrolyte, or gel polymer electrolyte, or solid ceramicelectrolyte) and first cathode active material and finally cathodecurrent collector (such as mesh or foil made of materials with very highelectronic conductivity such as aluminum, Ni, Ti, stainless steel); thisis how a battery is made today, now if we place a second active layer ofanode (cathode) between the said first active anode (cathode) layer andthe said separator then we have made the novel battery introduced here.It is noted that the second active material does not need to bephysically connected to the said current collector directly; and itdoesn't need to be in complete physical contact with the said firstactive material at all times.

The benefits of the novel design by the example that was introduced areexplained. As an example of the second anode layer consider LTO (lithiumtitanate) which is a known anode active material with very goodcyclability; however with the voltage of about 1.5 the energy density ofany cell with only LTO as anode is much less than that of withconventional graphite anode. On the other any battery with lithium metalanode is known to have very high energy density but can only last veryfew cycles due to lithium dendrite formation and electrolyte depletion(corrosion of lithium metal). It is also known that physical pressure onthe surface of lithium metal can significantly increase the cycle lifeof lithium metal anode batteries; however this is not practical in woundcells, cylindrical cells or any conventional format of batteries otherthan very small coin cells that implement a spring but has a very lowratio of active material to inactive material. Similar problem happenswith alloy anodes such as silicon, aluminum, Sn or other high capacityanode materials as they undergo large deformations when lithiated suchthat active material and electrolyte may be lost and thus the cycle lifeis very low. In an embodiment, the second layer of the anode activematerial helps with confining the first anode active material in placeby applying pressure on its surface. during lithiation; during dischargethe anode loses lithium which can result in creation of free spacebetween the current anode collector and the separator, this gap then canresult in poor lithium deposition during the charging of the battery asthere is no pressure to keep the surface of the lithium uniform duringlithium deposition or to keep the electric contact in place, especiallyuseful for silicon or Sn anode. By introducing the second layer ofactive material such as LTO (lithium titanate), this helps inmaintaining the pressure on the first active electrode material (Li, Si,Sn, etc.) by possibly at least one mechanism including 1—(Mechanical)the second active material layer such as LTO has higher elastic modulusthan electrolyte (many polymer electrolytes such as PEO, Balsara's grouppolymer, etc. are developed but none can have high elastic modulus andhigh ionic conductivity at the same time) and is mechanically strongerthan separator so dendrites can't get thicker after penetrating it bymaking the pores bigger; this means that the second layer ismechanically strong to apply pressure on the first electrode surface andthus help with better performance and cycling 2—(electrochemical) thesecond active layer such as LTO may show a different electrochemicalbehavior (e.g., LTO is at about 1.5 v wrt Li₊/Li) this means that anydendrite that may form on the lithium layer or anode current collectorhas to stop growing once it reaches the LTO layer and gives priority toLTO lithiation; even after the LTO lithiation stops the dendrite mayprefer not to grow as the lithiated LTO provides not only the physicalbarrier (mentioned earlier) but also it can change the electric fieldand also the electric conductivity at the lithium-LTO interface, thusmore uniform lithium deposition is possible.

The second electrode active material mentioned here can be a freestanding layer, can be a coating on the first active material layer orcan be a coating on the separator layer (separator includes polymer andsolid electrolytes). The said second active layer can be as thick as thefirst one, but preferably thinner (as the first one is the one with highenergy density and the second one is there to increase the safety andcycle life); it can be a few micrometers or tens of micrometers thick oreven tens or hundreds of nanometers thick). The second active layerfurther may have electronic conductivity or not, for example it can haveabout 10% conductive carbon or may not. As an example it can be a fewmircometers thick with no electronic conductivity. In some embodimentsthe first and second layers can be separated by a thin layer (e.g.,0.007 mm porous, woven, non-woven or perforated layer made of inertmaterials such as PE, PP, polyester, polyimide, TiO2, etc.). In someembodiments the secondary electrode layer has higher porosity than thefirst one. In some embodiments the secondary electrode (internal layerthat is closer to the opposite electrode) layer has lower electricconductivity than the primary electrode layer (external layer that isfurther from the opposite electrode), for example it has less conductivecarbon added.

Another example is a composite anode that is made of at least twodifferent anode active materials that may have different voltages andcapacities. For example an anode that is made of lithium metal and LTOanode (lithiated or delithated). The two different materials can make afibrous composite (e.g., LTO matrix and Lithium fibers), a laminatedcomposite (e.g., lithium layer on the current collector side and LTOlayer on the electrolyte side) or a coated-shell composite (e.g., LTOcoated on lithium), or lithium used as one of the binders-conductors ofthe other cathode (e.g. LTO powders made with addition-deposition oflithium metal). Upon recharging for example in an electrochemical cellwith LCO cathode and non-aqueous electrolyte, the LTO helps withmaintaining the structure of the anode and thus helps with the uniformdeposition of lithium metal (a known problem with conventional lithiummetal anode is that the structure is lost after discharging and thelithium metal may not deposit back uniformly leading to capacity lossand even shorting). Note that porous metal oxides such as LTO have goodlithium ion conductivity and allow the lithium ion to reach to the backof the current collector; it can also mechanically prevents lithiumdendrite shorting. Also note that, in the above example, upon rechargingthe cell may be charged in more than one step: first at about 1.5 voltscorresponding to LTO lithiation and then lithium deposition at 0 volt;on the other hand on discharge the LTO may delithate first beforelithium dissolution; this greatly enhances the cycle life of the batteryby mitigating dendrite formation and electrolyte consumption (SEIformation at about 0.7v); especially that in many applications only partof the energy of the battery is needed and thus the time at near 0voltage (wrt Li₊/Li) is reduced; it is known that less time at 0 voltageincrease the

LTO-Air Battery:

An air battery consisting of LTO anode and conventional air cathode isdisclosed. The electrolyte can be non-aqueous or can be aqueous. Theaqueous electrolyte has the advantage of easier handling andfabrication. The voltage is about 1.5 v and the capacity can be 100mAh/g of total weight of the battery, including oxygen. This givesenergy density of about 150 Wh/kg. The battery can be charged dischargedthousands of cycles.

Porous Metal Structure Anode:

An electrochemical cell (lithium battery, alkaline battery, leadbattery, air battery, flow battery, semisolid battery or fuel cell) withporous metal (such as silicon wool, aluminum wool or titanium wool) asanode is disclosed; conductive carbon can further be added to the poroussilicon to form an electronic conductive path of coating that is neededfor ionic (such as lithium ions and electrons forming lithiummetal-silicon anode) deposition (dissolution) inside the silicon poresduring the charging (discharging) of the cell. The electrochemcial cellcan be a rechargeable lithium ion battery. The benefit of porous silicon(such as those known in the art of porous silicon with at least 25%porosity, preferably closer but less than 75% porosity) is that poroussilicon structure acts as the host for the lithium during lithiation(charging the cell). The rationale for preferring about 75% porosity isthat silicon is known to undergo very large deformations upon lithiationthat increases its volume by a factor of 3, thus 75% porosity can act asa buffer and enable good cycle life by preventing the anode failure.Nano silicon has been tried by many different researchers and bettercyclablity is observed but it is very expensive; it is also preferred togrow the silicon nano-rods in a preferable crystallographic orientationsuch that the large deformation due to lithiation happens mostly in thefree space between the nano-rods (that is deformation happens in theplane with the rod orientation as the axis); and even doing so still theconductive carbon path may be lost after some cycles; also theelectrolyte loss is unavoidable (the silicon shape change still occurs).On the other hand porous silicon with about 70% porosity can avoid theelectrolyte loss and conductive carbon path loss because porous silicondoesn't need to change its shape and undergo large deformations duringcycling of the cell. The porous silicon can be prepared by methods knownin the art of silicon use such as by stain etching or anodization. Notethat this is different from conventional electrode making in whichparticles of the active material are adhered to each other by a binder(such as pvdf). There is no need for a binder in our electrode. Anotherproblem with silicon nanorods is that it is not flexible enough even atvery low thicknesses of electrodes (e.g. 0.100 mm) and thus making awound or cylindrical cell is not practical, on the other hand the poroussilicon can be easily deformed into a wound format for a cylindricalcell and thus has a cost advantage. See FIG. 12 for two perforatedaluminum foils with complementary hole patterns.

Example of rechargeable battery with lithium metal anode andconventional li-ion cathode (such as LiFePO4, NMC, NCA and LiCoO2),especially useful for high power applications. Example: rechargeablebattery with lithium metal anode, two perforated aluminum foils withcomplementary hole patterns (0.007 mm thickness, and 0.5 mm holediameter and 1 mm pitch), the two perforated aluminum foils

Another example is a rechargeable lithium metal battery with lithiatedcathode. The lithium metal anode is separated from the cathode with aporous-perforated elastomer (such as silicone, rubber or elasticelectrode binder materials known in the art, e.g., styrene-butadiene(ST-BD) copolymer and 2-ethylhexyl acrylate-acrylonitrile (2EHA-AN)copolymer, acryloxy perfluoropolyether, alginate, polyurethane) and ismade in the discharged mode that has the minimum thickness (e.g.,current collector thickness and possibly a thin layer of lithium thatperforms as the substrate for lithium deposition during charging). Thisway upon charging the lithium deposition results in compressive stressin the porous-perforated elastomer which itself applies pressure on thenewly deposited lithium and thus improves the performance of theelectrode and electrochemical cell. The cell also has an electrolyte andcan further have a separator (conventional separators or thoseintroduced by US Patent Publication no. 2013/0224632); the electrolytecan be aqueous, non-aqueous, polymer or solid electrolyte such as thoseknown in the art; electrolyte (liquid, gel, polymer or solid occupiesthe pores-apertures of the said elastomer layer.

Notes: the effect of pressure in these designs allows a smoother surfacewith fewer irregularities, on the electrodes. The effect of pressure maybe due to the change of the free energy; however, as too much pressuremay reduce the ionic conductivity of the pores in the separator layersor even electrodes, thus, there exist an optimum pressure range in whichthe best cell performance (smooth deposition on electrodes in additionto cycle life and rate capability) can be obtained. It is noteworthy tomention that very high pressure can result in a non-working condition,for example by hindering the electrolyte from covering the entiresurface of any of the electrodes. Any of the mentioned methods ordevices can further be combined with one or more of the other methods ordevices described here such as the separator bag to enhance the cyclicperformance of an electrochemical cell. The methods mentioned here canbe used for batteries, fuel cells, flow batteries, supercapacitors,ultracapacitors, or even as membranes in filtration industries such asfood, medical, oil, gas, water, etc.

Solid Electrolytes and Electrochemical Cells in which the SolidElectrolyte Powders (Such as NASICON, LISICON Type Ceramic Electrolytes)are Adhered to Each, Other Using a Binder.

The use of binders (such as pvdf, ptfe or other binders know n in theart) provides flexible, long-life, no-hole and low cost solidelectrolytes without the need of high temperature fabrication. Currentsolid electrolytes are made with powders treated at very hightemperatures which results in very expensive solid electrolytes whichhave to be thick to avoid pinholes and fragility. The high thicknessresults in higher ionic conductivity and no-deformability which makesthem impractical in industrial applications. Further our novel methodallows using different new materials such as LTO powder as components ofthe solid electrolyte. The amount of the binder can be about 5-10%. Asolvent (organic based or water based or any other solvent) can be usedto glue the powders to each other. Electrochemical cells suitable foruse with this embodiment, include lithium batteries, aluminum batteries,air batteries, alkaline batteries, fuel cells, flow batteries, semisolidbatteries and so on.

STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

All references cited throughout this application, for example patentdocuments including issued or granted patents or equivalents; patentapplication publications; and non-patent literature documents or othersource material; are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference, to theextent each reference is at least partially not inconsistent with thedisclosure in this application (for example, a reference that ispartially inconsistent is incorporated by reference except for thepartially inconsistent portion of the reference).

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferredembodiments, exemplary embodiments and optional features, modificationand variation of the concepts herein disclosed may be resorted to bythose skilled in the art, and that such modifications and variations areconsidered to be within the scope of this invention as defined by theappended claims. The specific embodiments provided herein are examplesof useful embodiments of the present invention and it will be apparentto one skilled in the art that the present invention may be carried outusing a large number of variations of the devices, device components,methods steps set forth in the present description. As will be obviousto one of skill in the art, methods and devices useful for the presentmethods can include a large number of optional composition andprocessing elements and steps.

When a group of substituents is disclosed herein, it is understood thatall individual members of that group and all subgroups, including anyisomers, enantiomers, and diastereomers of the group members, aredisclosed separately. When a Markush group or other grouping is usedherein, all individual members of the group and all combinations andsubcombinations possible of the group are intended to be individuallyincluded in the disclosure. When a compound is described herein suchthat a particular isomer, enantiomer or diastereomer of the compound isnot specified, for example, in a formula or in a chemical name, thatdescription is intended to include each isomers and enantiomer of thecompound described individual or in any combination. Additionally,unless otherwise specified, all isotopic variants of compounds disclosedherein are intended to be encompassed by the disclosure. For example, itwill be understood that any one or more hydrogens in a moleculedisclosed can be replaced with deuterium or tritium. Isotopic variantsof a molecule are generally useful as standards in assays for themolecule and in chemical and biological research related to the moleculeor its use. Methods for making such isotopic variants are known in theart. Specific names of compounds are intended to be exemplary, as it isknown that one of ordinary skill in the art can name the same compoundsdifferently.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural reference unless thecontext clearly dictates otherwise. Thus, for example, reference to “acell” includes a plurality of such cells and equivalents thereof knownto those skilled in the art, and so forth. As well, the terms “a” (or“an”), “one or more” and “at least one” can be used interchangeablyherein. It is also to be noted that the terms “comprising”, “including”,and “having” can be used interchangeably. The expression “of any ofclaims XX-YY” (wherein XX and YY refer to claim numbers) is intended toprovide a multiple dependent claim in the alternative form, and in someembodiments is interchangeable with the expression “as in any one ofclaims XX-YY.”

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described. Nothing herein is to be construed as anadmission that the invention is not entitled to antedate such disclosureby virtue of prior invention.

Every formulation or combination of components described or exemplifiedherein can be used to practice the invention, unless otherwise stated.

Whenever a range is given in the specification, for example, atemperature range, a time range, or a composition or concentrationrange, all intermediate ranges and subranges, as well as all individualvalues included in the ranges given are intended to be included in thedisclosure. As used herein, ranges specifically include the valuesprovided as endpoint values of the range. For example, a range of 1 to100 specifically includes the end point values of 1 and 100. It will beunderstood that any subranges or individual values in a range orsubrange that are included in the description herein can be excludedfrom the claims herein.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. In each instanceherein any of the terms “comprising”, “consisting essentially of” and“consisting of” may be replaced with either of the other two terms. Theinvention illustratively described herein suitably may be practiced inthe absence of any element or elements, limitation or limitations whichis not specifically disclosed herein.

One of ordinary skill in the art will appreciate that startingmaterials, biological materials, reagents, synthetic methods,purification methods, analytical methods, assay methods, and biologicalmethods other than those specifically exemplified can be employed in thepractice of the invention without resort to undue experimentation. Allart-known functional equivalents, of any such materials and methods areintended to be included in this invention. The terms and expressionswhich have been employed are used as terms of description and not oflimitation, and there is no intention that in the use of such terms andexpressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the invention claimed.Thus, it should be understood that although the present invention hasbeen specifically disclosed by preferred embodiments and optionalfeatures, modification and variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims.

1. An electrochemical cell comprising: a positive electrode; a negativeelectrode; one or more ionically conductive electrolytes positionedbetween said positive electrode and said negative electrode; and acomposite separator comprising at least one electronically insulatinglayer and at least one electronically conductive layer; said compositeseparator being positioned between said positive electrode and saidnegative electrode and being permeable to ionic charge carriers, but notelectronically conductive across the composite separator; wherein saidelectronically conductive layer undergoes deposition or electroplatingof ionic charge carriers or chemical reaction with a dendrite structureor an internal defect upon formation of an internal short between thenegative or the positive electrode and said electronically conductivelayer, the short formed by contact of the dendrite structure or theinternal defect with said electronically conductive layer.
 2. Theelectrochemical cell of claim 1, wherein the electronically conductivelayer is chemically reactive with the dendrite structure.
 3. Theelectrochemical call of claim 2, wherein the chemical reaction is analloying reaction.
 4. The electrochemical cell of claim 1, wherein thedendrite structure is a lithium or zinc dendrite. 5.-7. (canceled) 8.The electrochemical cell of claim 1, wherein said positive electrodecomprises a positive electrode active material, said negative electrodecomprises a negative electrode active material and said electronicallyconductive layer is provided between said insulating layer and saidpositive electrode or said negative electrode, thereby providing anadditional electronic path for the positive electrode active material orthe negative electrode active material.
 9. The electrochemical cell ofclaim 1 further comprising a second insulating layer, wherein saidelectronically conductive layer is provided between the two insulatinglayers. 10.-14. (canceled)
 15. The electrochemical cell of claim 1,wherein said electronically conductive layer is a perforated or porouslayer having a porosity greater than or equal to 30% and less than orequal to 90%. 16.-17. (canceled)
 18. An electrochemical cell comprising:a positive electrode comprising a positive electrode active material anda first current collector in electronic communication with the positiveelectrode active material, the first current collection furthercomprising a first external connection tab; a negative electrodecomprising a negative electrode active material and a second currentcollector in electronic communication with the negative electrode activematerial, the second current collector further comprising a secondexternal connection tab; one or more ionically conductive electrolytespositioned between said positive electrode and said negative electrode;and a composite separator comprising at least one electronicallyinsulating layer and at least one electronically conductive layer; saidcomposite separator being positioned between said positive electrode andsaid negative electrode and being permeable to ionic charge carriers,but not electronically conductive across the composite separator;wherein said electronically conductive layer further comprises a thirdexternal connection tab and is not provided in electrical contact withsaid positive electrode or said negative electrode in the absence ofsaid electrical short.
 19. The electrochemical cell of claim 18, furthercomprising a voltage or current monitoring circuit or voltage or currentapplying circuit connected between said electronically conductive layerand the negative or positive electrode. 20.-21. (canceled)
 22. Theelectrochemical cell of claim 18, wherein said positive electrodecomprises a positive electrode active material, said negative electrodecomprises a negative electrode active material and said electronicallyconductive layer is provided between said insulating layer and saidpositive electrode or said negative electrode, thereby providing anadditional electronic path for the positive electrode active material orthe negative electrode active material.
 23. The electrochemical cell ofclaim 18, further comprising a second insulating layer, wherein saidelectronically conductive layer is provided between the two insulatinglayers. 24.-29. (canceled)
 30. The electrochemical cell of claim 18,further comprising a solid electrolyte, wherein said electronicallyconductive layer is provided between the solid electrolyte and theinsulating layer.
 31. The electrochemical cell of claim 18, furthercomprising a solid electrolyte, wherein the electronically conductinglayer is porous and the solid electrolyte is provided in the pores ofthe electronically conducting layer. 32.-57. (canceled)
 58. Anelectrochemical system comprising the electrochemical cell of claim 18and further comprising a device for assessing state of charge or stateof health of the electrochemical cell, thereby allowing application ofvoltage or current through voltage or current applying circuit as afunction of state of charge and state of health of the cell, during eachcycle.
 59. A method of detecting the onset of a short in anelectrochemical cell; said method comprising the steps of: providingsaid electrochemical cell comprising: a positive electrode; a negativeelectrode; one or more ionically conducting electrolytes positionedbetween said positive electrode and said negative electrode; and acomposite separator comprising an electronically insulating and anelectronically conductive layer; said separator positioned between saidpositive electrode and said negative electrode such that said chargecarriers are able to be transported between said positive electrode andsaid negative electrode; and monitoring the voltage, current, capacityor a combination thereof of said electrochemical cell, wherein saidelectrochemical cell undergoes an observable change in voltage, current,capacity or a combination thereof between any two of the positiveelectrode, the negative electrode and the electronically conductivelayer upon formation of an electrical short between the electronicallyconductive layer and said positive electrode or said negative electrode.60. The method of claim 59, wherein the positive electrode comprises apositive electrode active material and a first current collector inelectronic communication with the positive electrode active material,the first current collection further comprising a first externalconnection tab, the negative electrode comprises a positive electrodeactive material and a second current collector in electroniccommunication with the negative electrode active material, the secondcurrent collection further comprising a second external connection tab,said electronically conductive layer further comprises a third externalconnection tab, and the voltage monitored is the voltage between theelectronically conductive layer and the positive electrode or thenegative electrode.
 61. The method of claim 59, further comprising thestep of changing at least one operating condition of saidelectrochemical cell in the event of detection of said observable changein voltage, current, capacity or a combination thereof, wherein saidoperating condition is selected from the group consisting of a dischargerate, a load on said electrochemical cell, an voltage between thepositive electrode and the negative electrode, and a temperature of saidelectrochemical cell.
 62. A method of reducing dendrite growth in anelectrochemical cell; said method comprising the steps of: a) providingsaid electrochemical cell comprising: a positive electrode; a negativeelectrode; one or more electrolytes positioned between said positiveelectrode and said negative electrode; said one or more ionicallyconductive electrolytes; and a composite separator comprising anelectronically insulating and an electronically conductive layer; saidseparator positioned between said positive electrode and said negativeelectrode such that said charge carriers are able to be transportedbetween said positive electrode and said negative electrode; andcharging said electrochemical cell, wherein said electronicallyconductive layer undergoes deposition, electrochemical plating or alloyreaction with a dendrite structure formed during charge between theelectronically conductive layer and said positive electrode, negativeelectrode or both.
 63. The method of claim 62, wherein said deposition,electrochemical plating or alloy reaction stops or decrease the rate ofgrowth of said dendrite structure or internal defect.
 64. A method ofoperating an electrochemical cell, the method comprising the steps of:providing said electrochemical cell comprising: a positive electrode; anegative electrode; one or more ionically conductive electrolytespositioned between said positive electrode and said negative electrode;and a composite separator comprising at least one electronicallyinsulating layer and at least one electronically conductive layer; saidcomposite separator being positioned between said positive electrode andsaid negative electrode and being permeable to ionic charge carriers,but not electronically conductive across the composite separator;charging, discharging or charging and discharging the electrochemicalcell, thereby inducing a surface charge on the surface of theelectronically conductive layer.
 65. The method of claim 64, whereinsaid electronically conductive layer provides an electric field adjacentto and within said positive electrode, said negative electrode or both,thereby providing uniform ion deposition into said positive electrode,said negative electrode or both during charging or discharging of saidelectrochemical cell.
 66. (canceled)
 67. The method of claim 64, furthercomprising changing at least one operating condition of saidelectrochemical cell in the event of detection of said observable changein voltage. 68.-70. (canceled)
 71. The electrochemical call of claim 18,further comprising a voltage or current applying circuit connectedbetween each of said electrochemically conductive layers and one of thepositive or the negative electrode, thereby allowing modification of theelectric field and the performance of the electrochemical cell.
 72. Themethod of claim 64, wherein the positive electrode comprises a positiveelectrode active material and a first current collector in electroniccommunication with the positive electrode active material, the firstcurrent collection further comprising a first external connection tab;the negative electrode comprises a negative electrode active materialand a second current collector in electronic communication with thenegative electrode active material, the second current collector furthercomprising a second external connection tab; electronically conductivelayer further comprises a third external connection tab and is notprovided in electrical contact with said positive electrode or saidnegative electrode; and the method further comprises the step ofapplying a voltage or current between the third external connection taband one of the first or the second external connection tab, therebyredistributing active material in the cell.
 73. The method of claim 64,wherein the positive electrode comprises a positive electrode activematerial and a first current collector in electronic communication withthe positive electrode active material, the first current collectionfurther comprising a first external connection tab; a negative electrodecomprises a negative electrode active material and a second currentcollector in electronic communication with the negative electrode activematerial, the second current collector further comprising a secondexternal connection tab; the cell further comprises a layer ofelectrolyte additive attached to said electronically conductive layer;and the method further comprises the step of applying a voltage orcurrent between the third external connection tab and one of the firstor the second external connection tabs, thereby releasing electrolyteadditive into the electrolyte of the cell.